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New Simplified Chemistry Class 10 ICSE Solutions – Study Of Compounds: Ammonia

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Questions
2001

Question 1.
State what do you observe when :
Neutral litmus solution is added to an alkaline solution.
Answer:
The litmus solution turns to blue.

Question 2.
Name (formula is not acceptable) the gas produced in the following reaction :
Warming ammonium sulphate with sodium hydroxide solution.
Answer:
Ammonia gas.

Question 3.
Write the equation for the preparation of NH3 from ammonium chloride and calcium hydroxide.
Answer:
2NH₄Cl + Ca(OH)₂ → CaCl₂ + 2NH₃ + 2H₂O

Question 4.
What are the products formed when ammonia is oxidized with copper oxide.
Answer:

2002

Question 1.
From the following gases – ammonia, chlorine, hydrogen chloride, sulphur dioxide, select the gas that turns moist red litmus paper blue.
Write the equation for the reaction – when the gas is passed over heated CuO.
Answer:
Ammonia gas.
3CuO + 2NH₃ → 3Cu + N₂ + 3H₂O

2003

Question 1.
Name a gas whose solution in water is alkaline.
Answer:
Ammonia

Question 2.
How would you distinguish between Zn²⁺ and Pb²⁺ using ammonium hydroxide solution.
Answer:
Zinc salt gives white gelatinous ppt. and Pb²⁺ gives chalky white ppt. with ammonium hydroxide.

Question 3.
Write the equation for the formation of ammonia by the action of water on mangesium nitride.
Answer:
Mg₃N₂ + 6H₂O → 2NH₃ + 3Mg (OH)₂

Question 4.
How is ammonia collected. Why is ammonia not collected over water.
Answer:
Ammonia gas is lighter than air and hence collected by the downward displacement of air.
Ammonia is not collected over water because it is highly soluble in water.

Question 5.
Which compound is normally used as a drying agent for ammonia.
Answer:
Quicklime(Calcium oxide CaO).

2004

Question 1.
From the gases ammonia, hydrogen chloride, hydrogen sulphide, sulphur dioxide – Select the following :

1. When this gas is bubbled through copper sulphate soln., a deep blue coloured solution is formed.
2. This gas burns in oxygen with a green flame.

Answer:

1. ammonia
2. ammonia

Question 2.
Write the equation for the reaction in the Haber’s process that forms ammonia.
Answer:

Question 3.
State the purpose of liquefying the ammonia produced in the process.
Answer:
By liquefying ammonia, it can be easily seperated from unreacted N₂ and H₂ gases.

Question 4.
Write an equation for the reaction of chlorine with excess of ammonia.
Answer:

2005

Question 1.
Name the ion other than ammonium ion formed when ammonia dissolves in water.
Answer:
Hydroxyl ion (NH₃ + H₂O → NH⁺₄ + OH^– )

Question 2.
Write the equations for the following reactions which result in the formation of ammonia.

1. A mixture of ammonium chloride and slaked lime is heated.
2. Aluminium nitride and water.

Answer:

2006

Question 1.
Select the correct compound from the list given — Ammonia, Copper oxide, Copper sulphate, Hydrogen chloride, Hydrogen sulphide, Lead bromide — which matches the description given below :
The compound is not a metal hydroxide, its aqueous solution is alkaline in nature.
Answer:
Ammonia.

Question 2.
From the list of substances given — Ammonium sulphate, Lead carbonate, Chlorine, Copper nitrate, Ferrous sulphate — State :
A compound which on heating with sodium hydroxide produces a gas which forms dense white fumes with hydrogen chloride.
Answer:
Ammonium sulphate.

Question 3.
State what is observed when excess of ammonia is passed through an aq. solution of lead nitrate.
Answer:
Chalky white insoluble ppt. is formed.

Question 4.
Name the substance used for drying ammonia,
Answer:
Quick lime (CaO).

Question 5.
Write a balanced chemical equation to illustrate the reducing nature of ammonia.
Answer:
Reducing nature of ammonia.
2NH₃ + 3CuO → 3Cu + 3H₂ + N₂ (g)

Question 6.
With reference to Haber’s process for the preparation of ammonia, write the equation and the conditions required.
Answer:

Conditions for maximum yield of ammonia

1. High Pressure (700-900 atm)
2. Optimum temperature (450-500°C)
3. Use of a catalyst : Iron (Fe) and use of a promotor : Molybdenum (Mo)

2007

Question 1.
Write a balanced equation for the following reaction :
Ammonium sulphate from ammonia and dilute sulphuric acid.
Answer:

Question 2.
Give equation for – reaction in which NH₃ is oxidized by :

1. a metal oxide ;
2. a gas which is not oxygen.

Answer:

Question 3.
You enter a laboratory after a class has completed the Fountain Experiment. How will you be able to tell whether the gas used in the experiment was hydrogen chloride or ammonia.
Answer:
If the colour of the litmus solution in the round bottomed flask is blue the gas used was ammonia and if the colour of the litmus solution in the round bottomed flask is red, the gas used was hydrogen chloride. This is because hydrogen chloride(aq) is acidic in nature and turns purple litmus solution red and ammonia (aq) is basic in nature and turns purple neutral litmus solution blue.

2008

Question 1.
Ammonia can be obtained by adding water to : [Select the correct word]
A Ammonium chloride
B Ammonium nitrite
C Magnesium nitride
D Magnesium nitrate
Answer:
C Magnesium nitride

Question 2.
Name : An alkaline gas A which gives dense white fumes with hydrogen chloride.
Answer:
NH₃ (Ammonia)

Question 3.
Write the equation for the following reaction : Aluminium nitride and water.
Answer:

Question 4.
Complete the table relating to an important industrial processes. [Output refers to the product of the process].

Answer:

2009

Question 1.
Name the gas – that burns in oxygen with a green flame.
Answer:
Ammonia (NH₃)

Question 2.
Write a fully balanced equation for the following : Magnesium nitride is treated with warm water.
Answer:

Question 3.
Identity the substances ‘Q’ based on the information given :
The white crystalline solid Q is soluble in water, it liberates a pungent smelling gas when heated with sodium hydroxide solution.
Answer:
Q is Ammonium chloride and pungent smelling gas is ammonia.

2010

Question 1.
Complete the blanks (a) to (e) in the passage given, using the following words.
(Ammonium, reddish brown, hydroxyl, nitrogen dioxide, ammonia, dirty green, alkaline, acidic) in the presence of a catalyst, nitrogen and hydrogen combine
to give (a) _____ gas. When the same gas is passed through water, it forms a solution which will be _____ (b) in nature, and will contain the ions (c) _____ and (d) _____ (e) _____ coloured precipitate of iron [II] hydroxide is formed when the above solution is added to iron [II] sulphate solution, sssssss
Answer:

(a) Ammonia
(b) Alkaline
(c) Ammonium
(d) Hydroxyl
(e) Dirty green

Question 2.
State your observation when – in the absence of a catalyst ammonia gas is burnt in an atmosphere of oxygen.
Answer:
Greenish yellow flame is observed.

Question 3.
Give the equation for the reaction : ammonium chloride is heated with sodium hydroxide.
Answer:
NH₄Cl + NaOH → NaCl + NH₃ + H₂O

Question 4.
In the manufacture of ammonia.

1. Name the process.
2. State the ratio must the reactants taken ?
3. State the catalyst used.
4. Give the equation for the manufacture of the gas ammonia.

Answer:

Question 5.
Write a relevant equation, to show that ammonia can act as a reducing agent
Answer:
2NH₃ + 3Cl₂ → N₂ + 6HCl

Question 6.
Name two gases you have which can be used to study the fountain experiment.
State the common property demonstrated by the fountain experiment ?
Answer:
Two gases which are used to study the fountain experiment are Hydrogen chloride gas (HCl) and Ammonia (NH3)
The common property of these two gases demonstrated by the fountain experiment is the solubility of gases

2011

Question 1.
State what is observed when – Ammonium hydroxide is first added in a small quantity and then in excess to a solution of copper sulphate.
Answer:
On adding ammonium hydroxide in small amount, pale blue precipitates will appear. On adding ammonium hydroxide in excess, blue precipitates will dissolve forming deep blue solution.

Question 2.
The diagram shows set up for the laboratory preparation of a pungent alkaline gas.

1. Name the gas collected in the jar.
2. Write the balanced equation for the above preparation
3. State how the gas is collected?
4. Name the drying agent used.
5. State how you will find out that the jar is full of pungent gas?

Answer:

1. Ammonia (NH₃)
2. NH₄ Cl + Ca (OH)₂ → CaCl₂ + 2H₂O + 2NH₃ ↑
3. Downward displacement of air
4. Quicklime (CaO)
5. Bring a rod dipped in HCl near it. Dense white fumes of ammonium chloride will be formed.

Question 3.
Write a balanced chemical equation – Chlorine reacts with excess of ammonia.
Answer:

Question 4.
State your observation when – Water is added to the product formed, when aluminium is burnt in a jar of nitrogen gas.
Answer:
Pungent smelling and alkaline gas (NH₃) is evolved.

2012

Question 1.
Name the gas produced when excess ammonia reacts with chlorine.
Answer:
Nitrogen.

Question 2.
Rewrite the correct statement with the missing word/s Magnesium nitride reacts with water to liberate ammonia.
Answer:
Magnesium nitride reacts with warm water to liberate ammonia along with magnesium hydroxide.

Question 3.
Give balanced equation for the reaction : Ammonia and Oxygen in the presence of a catalyst.
Answer:

Question 4.
The following questions are based on the preparation of ammonia gas in the laboratory:

1. Explain why ammonium nitrate is not used in the preparation of ammonia.
2. Name the compound normally used as a drying agent during the process.
3. How is ammonia gas collected ? Explain why it is not collected over water.

Answer:

1. Ammonium nitrate does not undergo a reversible sublimation reaction, it melts and then decompses into nitrogen oxide gas and water vapour. Thus it is not used in the preparation of ammonia.
   NH₄NO₃ → N₂O + 2H₂O
2. Calcium oxide
3. Ammonia is collected in an inverted dry gas jar by downward displacement of air.
   It is highly soluble in water and hence cannot be collected by downward displacement of water.

2013

Question 1.
State one appropriate observation for :
Excess of chlorine gas is reacted with ammonia gas.
Answer:
A yellow explosive liquid (Nitrogen trichloride) is formed.

Question 2.
Nitrogen gas can be obtained by heating :

(a) Ammonium nitrate
(b) Ammonium nitrite
(c) Magnesium nitric
(d) Ammonium chloride

Answer:

(b) Ammonium nitrite

Question 3.
State two relevant observations for :
Ammonium hydroxide solution is added to zinc nitrate solution in minimum quantities and then in excess.
Answer:
A white gelatin like precipitate of zinc hydroxide is formed which dissolves in excess of ammonium hydroxide.

Question 4.
Give balanced equations for :
Reduction of hot Copper (II) oxide to copper using ammonia gas.
Answer:

Question 5.
Copy and complete the following table relating to im¬portant industrial process :

Answer:

Question 6.
Identify : An alkaline gas which produces dense white fumes when reacted with HCl gas.
Answer:
Ammonia gas.

2014

Question 1.
Fill in the blank from the choices given in bracket : Ammonia gas is collected by _____ (upward displacement of air, a downward displacement of water, a downward displacement of air)
Answer:
Ammonia gas is collected by a downward displacement of air.

Question 2.
Write balanced equation for : Action of warm water on magnesium nitride.
Answer:
Action of warm water on magnesium nitride.

Question 3.
Distinguish between the following pairs of compounds using the test given within bracket :

1. Iron(II)sulphate and iron (III) sulphate (using ammonium hydroxide)
2. A lead salt and a zinc salt (using excess ammonium hydroxide)

Answer:

Question 4.
State your observation : Calcium hydroxide is heated with ammonium chloride crystals.
Answer:

ammonia gas is evolved which fumes strongly in moist air.

Question 5.
Name the other ion formed when ammonia dissolves in water. Give one test that can be used to detect the presence of the ion produced.
Answer:

Question 6.
State the conditions required for : Catalytic oxidation of ammonia to nitric oxide.
Answer:
Catalytic oxidation of ammonia to nitric oxide.

Conditions for catalytic oxidation of ammonia to nitric oxide : Platinum catalyst and 800°C temperature.

2015

Question 1.
From the list the gases — Ammonia, ethane, hydrogen chloride, hydrogen sulphide, ethyne
Select the gas which is used as a reducing agent in reducing copper oxide to copper.
Answer:
Hydrogen

Question 2.
State one relevant observation — Ammonia gas is burnt in an atmosphere of excess oxygen.
Answer:
Ammonia gas bums to form nitrogen gas and steamy fumes of water.

Question 3.
A metal ‘X’ has valency 2 and a non-metal ‘Y’ has a valency 3.
If ‘Y ’ is a diatomic gas, write an equation for the direct combination of X and Y to from a compound.
Answer:
The equation for the direct combination of X and Y to form a compound is

Question 4.
Give balanced chemical equations —

1. Lab. preparation of ammonia using an ammonium salt.
2. Reaction of ammonia with excess chlorine.
3. Reaction of ammonia with sulphuric acid.

Answer:

1. Ammonia is prepared in the laboratory by using ammonium chloride.
   
2. When ammonia reacts with excess of chlorine, it forms nitrogen trichloride and HCl
   
3. Ammonia reacts with sulphuric acid to form ammonium sulphate.
   

2016

Question 1.
Write balanced equations for :

1. Action of warm water on AIN.
2. Excess of ammonia is treated with chlorine.
3. An equation to illustrate the reducing nature of ammonia.

Answer:

Question 2.
Name the gas evolved when the following mixtures are heated :

1. Calcium hydroxide and Ammonium chloride.
2. Sodium nitrite and Ammonium chloride.

Answer:

1. Ammonia gas
2. Nitrogen gas

2017

Question 1.
Write the balanced chemical equation for each of the following –

1. Reaction of ammonia with heated copper oxide.
2. Laboratory preparation of ammonia from ammonium chloride.

Answer:

Question 2.
State one relevant observation for the following reaction – Burning of ammonia in air.
Answer:
Ammonia bums with a yellowish green flame.

Question 3.
Certain blanks spaces are left in the following tables as C, D & E. Identify each of them.

Answer:

C : Reactants are Magnesium nitride(Mg₃N₂) and water(H₂O).
D : Drying agent is anhydrous calcium oxide (Quick lime).
E : NH₃ gas is collected by the downward displacement of air.

Question 4.
Give a balanced chemical equation for each of the following –

1. Catalytic oxidation of ammonia.
2. Reaction of ammonia with nitric acid.

Answer:

Additional Questions

Question 1.
State why nitrogenous matter produces ammonia. State a liquid source of ammonia.
Answer:
When nitrogenous matter (such as animal and vegetable protiens) decays in the absence of air, the putrefying bacteria on the organic matter in the soil or ammonifying bacteria in organic matter produces ammonia.
The liquid souce of ammonia is decaying urine of animals.

Question 2.
Give the word equation and balanced molecular equation for the laboratory preparation of ammonia from NH4Cl and calcium hydroxide.
Answer:
Ammonium Chloride + Calcium Hydroxide → Calcium Chloride + Water + Ammonia

Question 3.
Convert ammonium sulphate to ammonia using two different alkalis.
Answer:

Question 4.
State why ammonia is not obtained in the laboratory from NH₄NO₃ and NaOH.
Answer:
Ammonium nitrate on heating decomposes explosively with the formation of nitrous oxide and water.

Question 5.
State the method used with reasons for drying and collecting ammonia gas.
Answer:
Calcium oxide (quick lime) is used for drying ammonia. It is because, calcium oxide being basic in nature does not react chemically with ammonia.
CaO + H₂O → Ca(OH)₂
Chemicals such as CaCl₂ (anhydrous), P₂O₅ and cone H₂SO₄ are not used for drying ammonia, because they react chemically with it as shown in the equation below :

Ammonia is collected by downward displacement of air. Ammonia gas is highly soluble in water, as such it cannot be collected over water. Further, ammonia is lighter than air. As such ammonia is collected by downward displacement of air.

Question 6.
State how you would convert (i) Mg (ii) Ca (iii) Al – to ammonia.
Answer:

Question 7.
Give a balanced equation with all conditions to obtain NH₃ from N₂ and H₂.
Answer:

Conditions for maximum yield of ammonia :

• Pressure : 200-900°C (High pressure)
• Temperature : 450-500°C (Optimum temperature)
• Catalyst : Finely divided iron, Fe
• Promotor : Molybdenum, Mo

Question 8.
State two physical properties of NH₃ which enable separation of NH₃ from a mixture of NH₃, N₂ and H₂.
Answer:

1. Ammonia liquifies at a pressure 8 atmosphere at -33°C, but not hydrogen and nitrogen.
2. Ammonia is extremely soluble in water, but not hydrogen and nitrogen.

Question 9.
Compare the density of ammonia with that of air. Name two gases lighter than ammonia.
Answer:
The vapour density of ammonia is 8.5 and that of air is 14.4. The two gases lighter than ammonia are

1. hydrogen
2. helium.

Question 10.
‘Ammonia is highly soluble in water’. Name two other gases showing similar solubility.
Answer:
The other highly soluble gases in water are :

1. Hydrogen chloride
2. Sulphur trioxide.

Question 11.
Name the experiment and state its procedure to demonstrate the high solubility of ammonia.
Answer:
Highly solubility of ammonia can be shown by Fountain Experiment.
To demonstrate the high solubility of ammonia gas in water.

Apparatus :

1. Round bottomed flask filled with ammonia gas.
2. Mouth of the flask with a rubber stopper with two holes, one for jet tube and other for dropper containing water.
3. Trough below contains red litmus solution.

Procedure :

1. The dropper containing water is squeezed and few drops of water enters the flask.
2. Ammonia gas present in the flask gets dissolved in water due to its high solubility, which creates a partial vacuum in the flask.
3. Since outside pressure is higher, so red litmus solution rush up the jet tube and emerge as a fountain. (Ammonia gas being basic changed red litmus blue.)
   Ammonia gas is lighter than air, hence it is collected by downward displacement of air.
4. Easily liquified at low temperatures.
5. Liquid ammonia boils at – 33.5°C
6. Solid ammonia melts at – 77.5°C

Question 12.
Give an equation for the burning of ammonia in oxygen. State the observation seen.
Answer:
Ammonia bums in the atmosphere of oxygen with a pale blue flame, forming nitrogen gas and water vapour.

Question 13.
Convert ammonia to nitric oxide by catalytic oxidation of ammonia. State all conditions.
Answer:
When a mixture of 2 (vols.) of oxygen and l(vols.) of ammonia is passed over platinum gauze maintained at 800°C, it reacts to form nitric oxide and water vapour.

• Conditions for the reaction : Ostwald’s process
• Temperature : 800°C
• Catalyst : Platinum (Pt)

Question 14.
Draw a simple diagram for the catalytic oxidation of ammonia in the laboratory.
Answer:

Question 15.
Give reasons for the observation seen during catalytic oxidation of ammonia.
Answer:
The colourless nitric oxide formed undergoes further oxidation to give reddish brown vapours of nitrogen oxide.
The platinum(catalyst) continues to emit a reddish glow even after the heating is discontinued since the catalytic oxidation of ammonia is an exothermic reaction.

Question 16.
Name an industrial process which involves ammonia, oxygen and a catalyst as its starting reactants.
Answer:
The industrial process is called Ostwald’s process for preparing nitric acid.

Question 17.
State what an aqueous solution of NH₃ is called. State how it is prepared giving reasons.
Answer:
The aqueous solution of ammonia is chemically ammonium hydroxide(NH₄OH) (Liquor Ammonia).
It is prepared by connecting the delivery tube of the apparatus generating ammonia with an inverted funnel whose rim is just dipping in water contained in beaker.
This arrangement provides

1. large surface area for the absorption of ammonia and
2. prevents back suction
   NH₃ + H₂O → NH₄ OH

Question 18.
State why an aq. soln. of NH₃

1. turns red litmus blue
2. is a weak base and a weak electrolyte.

Answer:

1. Ammonia on dissolving in water furnishes ammonium (NH₄⁺) ions and hydroxyl (OH^–) ions.
   
   The presence of OH^– turns the red litmus blue.
2. When ammonia dissolves in water, it forms ammonium hydroxide. The ammonium hydroxide dissociates to NH₄⁺ ions and OH^– ions.
   However, the degree of dissociation of ammonium hydroxide molecules is very low. Thus, due to the presence of few OH- ions it is a weak base, as well as weak electrolyte.

Question 19.
State two different methods of preparing NH₄Cl using hydrochloric acid.
Answer:

1. When ammonium hydroxide is treated with hydrochloric acid, neutrilisation reaction takes place with formation of Ammonium chloride
   NH₄OH + HCl (dil.) → NH₄Cl + H₂O
2. When ammounium carbonate is treated with hydrochloric acid, it forms ammonium chloride, carbon dioxide and water.
   (NH₄)₂ CO₃ + 2HCl (dil.) → 2NH₄Cl + CO₂ + H₂O

Question 20.
Convert (i) ammonia (ii) ammonium hydroxide to an ammonium salt using (a) HNO₃ (b) H₂SO₄.
Answer:

Question 21.
State a reason why reaction of liquor ammonia with nitric acid is a neutralization reaction.
Answer:
Liquor ammonia is a saturated solution of ammonia in water. Ammonia, NH₃ dissolves in water to give ammonium hydroxide which dissociates partially to give NH₄⁺ and OH^– ions. Due to presence of OH^– ions, ammonium hydroxide acts as an alkali.

The reaction between an acid (nitric acid) and an alkali or base is a neutralisation reaction.

Hence, the reaction between liquor ammonia and nitric acid is a neutralisation reaction.

Question 22.
State why an aqueous solution of ammonia (NH₄OH) is used for identifying cations.
Answer:
Because of its colour and solubility in excess NH₄OH.

Question 23.
State how NH₄OH is used for identify :

1. Fe²⁺
2. Fe³⁺
3. pb²⁺
4. Zn²⁺
5. Cu²⁺ cations.

Give also a balanced equation in each case for a known example.
Answer:

Question 24.
State why the blue ppt. formed on addition of NH₄OH to CuSO₄ soln. dissolves to give a deep blue solution with excess of NH₄OH. Give an equation for the reaction. State why Zn(OH)₂ is soluble in excess of NH₄OH.
Answer:
CuSO₄ when reacts with excess of ammonia it produces needle shape crystals of tetraammine copper(II) sulphate complex which possess a beautiful deep blue colour.

Question 25.
Give balanced equations for the reducing reactions of ammonia with
(i) copper (II) oxide, (ii) lead (II) oxide, (iii) chlorine using, (a) excess NH₃, (b) excess Cl₂.
Answer:

Question 26.
State five tests for ammonia where a colour change is involved.
Answer:
Tests for ammonia :

1. Ammonia turns red (or purple) litmus solution to blue.
2. Ammonia turns methyl orange solution to yellow.
3. Ammonia turns phenolphthalein (colourless) solution to pink.
4. Ammonia turns Nesseler’ reagent (colourless) solution to pale brown.
5. Ammonia (when in excess) gives a deep blue coloured solution with CuSO₄ (aq.)

Question 27.
State (i) a light neutral gas (ii) an acid (iii) an explosive (iv) a fertilizer — obtained from ammonia.
Answer:

1. Hydrogen
2. Nitric acid
3. NH₄NO₃
4. Ammonium sulphate.

Question 28.
Name an ammonium salt which is a constituent of (a) smelling salts (b) dry cells.
Give reasons for the use of the named ammonium salt for the same.
Answer:

(a) Smelling salts : Ammonium carbonate, (NH₄)₂CO₃ is used as smelling salt. It is an unstable white solid decomposes to give pungent smellingNH₃ gas.
(NH₄)₂CO₃ → 2NH₃ + CO₂ + H₂O
The pungent smelling NH₃ gas revives a fainted person. (NH₄)₂CO₃ is always kept in a tightly closed container to prevent it from decomposition.
(b) Dry cells : Ammonium chloride(NH₄Cl) is used in dry cells. It oxidises Zn to Zn²⁺ ions. The electrons so produced constitute the electric current.

Question 29.
Give one use with reason of

1. an aqueous solution of NH₃
2. liquefied NH₃.

Answer:
(i) Use of an Aqueous solution of Ammonia (NH₃) : An aqueous solution of NH₃ is called liquor ammonia. Being a base, it can easily emulsify oils and fats. Therefore, it is used for removing oil and fat stains from clothes carpets, upholstery etc. It is also used for cleaning window panes, porcelain articles etc.
(ii) Use of Liqueified Ammonia (NH₃) : Liquid ammonia is used as refrigerant i.e. for producing low temperature. This is due to the following reasons:

(a) It is highly volatile.
(b) It can be easily liquefied under high pressure and low temperature.
(c) It’s latent heat of evaporation is very high.

Question 30.
State what are chlorofluorocarbons and give their use. Give a reason why they are ozone depleting. State a suitable alternative to chlorofluorocarbons which are non-ozone depleting.
Answer:
Chlorofluorocarbons (CFC’s) are compounds of carbon with chlorine or fluorine.
CFC are chemicals which like liquefied ammonia gas are used in refrigeration gas. They are also used as coolants in refrigeration and A/c Plants and aerosol sprays and cleansing agents.
These CFC’s deplete ozone layer and also contribute to global warming. Thus these CFC’s are harmful to life. The CFC’s are decomposed by ultraviolet rays coming from sun to produce highly reactive chlorine atoms i.e. free Cl radicals.
Suitable alternatives to chloroflurocarbons which are not depleting ozone are :
HCFC – Hydrochloroflurocarbons; and HFC – 125 Hydrochloroflurocarbons ; which act as a substitute for CFCs, which are non-ozone depleting.

Unit Test Paper 7b —Ammonia

Q.1. Choose the letter corresponding to the correct answer from — A : NO₂, B : NO, C : N₂, D : N₂O.
The gas obtained when –
1. Dry ammonia and dry oxygen gas are ignited together.
2. Ammonia is passed over heated litharge.
3. A greenish yellow gas reacts with excess ammonia.
4. (a) Dry NH₃ and O₂ are passed over heated Pt.
(b) The gaseous product obtained is further oxidised.
5. Ammonium nitrite undergoes thermal decomposition.
Answer:

1. C(N₂)
2. C(N₂)
3. C(N₂)
4. (a) B(NO),(b) A(NO₂)
5. D(N₂O)

Q.2. State the colour of :

Question 1.
Phenolphthalein solution after passage of ammonia through it.
Answer:
Colourless phenolphthalein changes to pink colour.

Question 2.
Copper (II) hydroxide solution after-addition of ammonium hydroxide in excess to it.
Answer:
The pale blue precipitate turns into a deep blue coloured solution.

Question 3.
The flame obtained on burning dry ammonia in oxygen.
Answer:
Greenish yellow flame.

Question 4.
The solution obtained on addition of excess ammonium hydroxide to zinc sulphate solution.
Answer:
White gelantinous precipitate dissolves.

Question 5.
The vapours obtained when ammonia-oxygen gas mixture is passed over heated Pt.
Answer:
The colourless NO gas first produced is further oxidises to brown coloured NO₂.

Q.3. Give balanced equations for the following conversions — A, B, C, D and E.

Answer:

Q.4. Give reasons for the following.

1. An aqueous solution of ammonia acts as a weak base.
2. A mixture of ammonium nitrate and slaked lime are not used in the lab. preparation of ammonia gas.
3. Finely divided iron catalyst does not affect the percentage yield of ammonia in Haber’s process.
4. Ammonium salts are formed when ammonia reacts with dilute acids in the gaseous or aq. medium.
5. Aqueous solution of lead and zinc nitrate can be distinguished using an aqueous solution of ammonia.

Answer:

1. Ammonia molecule contains a lone pair of electrons on N- atom, which accepts a proton from water, and forms ammonium ion and hydroxide ion, this makes ammonia solution alkaline and thus, it acts as a base.
   NH₃+ H₂O → NH₄⁺ + OH^–
   However, as the concentration of the hydroxyl ions that are furnished is less, therefore aqueous solution of ammonia acts as a weak base.
2. Because ammonium nitrate is explosive and decomposes itself.
3. Formation of NH₃ from N₂ and H₂ in haber’s process is a reversible reaction. In a reversible reaction, a catalyst does not increase the yield of the product. It only helps in attaining the equilibrium in a shorter time.
   
4. Ammonia in gaseous form neutralises acids to form salts.
5. Zinc nitrate forms white gelatinous ppt. while lead nitrate forms chalky white ppt.

Q.5. Complete the statements by selecting the correct word from the words in brackets.

1. The salt solution which does not give an insoluble precipitate on addition of ammonium hydroxide in small amount is _____ (Mg(NO₃)₂ / NaNO₃/Cu(NO₃)₂]
2. The alkaline behaviour of liquor ammonia is due to the presence of _____ ions, (ammonium / hydronium / hydroxyl)
3. Ammonia in the liquefied form is _____ (acidic / basic / neutral)
4. Ammonia reduces chlorine to _____ (nitrogen / hydrogen chloride / ammonium chloride)
5. The chemical not responsible for ozone depletion is _____ [methyl chloride / ammonia / chloroflourocarbons]

Answer:

1. NaNO₃
2. Hydroxyl
3. basic
4. Ammonium chloride .
5. Ammonia

Q.6. Select the most probable substance from A, B, C, D and E which need to be added to distinguish :


Answer:

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New Simplified Chemistry Class 10 ICSE Solutions – Study Of Compounds: Hydrogen Chloride

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Questions
2005

Question 1.
Write balanced equations for the following reactions :

1. Copper oxide and dilute Hydrochloric acid.
2. Manganese (IV) oxide and concentrated Hydrochloric acid.

Answer:

Question 2.

1. Name the experiment illustrated aside.
2. Which property of hydrogeii chloride is demonstrated by this experiment.
   
3. State the colour of the water that has entered the round-bottomed flask.

Answer:

1. Fountain experiment.
2. Hydrogen chloride is soluble in water.
3. Red.

2006

Question 1.
From the list — Ammonia, Copper oxide, Copper sulphate, Hydrogen chloride, Hydrogen sulphide, Lead bromide — select the compound which can be oxidized to chlorine.
Answer:
Hydrogen chloride

Question 2.
Write balanced chemical equation for the reaction of zinc and dilute hydrochloric acid.
Answer:
Zn + 2HCl → ZnCl₂ + H₂

Question 3.
State what is observed when hydrochloric acid is added to silver nitrate solution.
Answer:
A white ppt. of silver chloride is formed.

Question 4.
Write a balanced chemical equation for the reaction of calcium bicarbonate and dil. hydrochloric acid.
Answer:
Ca(HCO₃)₂ + 2HCl → CaCl₂ + 2CO₂ + 2H₂O.

2007

Question 1.
Write a balanced equation for the following reaction :
Sodium chloride from sodium carbonate solution and dilute hydrochloric acid.
Answer:
Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂

Question 2.
Of the two gases, NH₃ and HCl, which is more dense.
Name the method of collection of this gas.
Answer:
Hydrogen chloride gas ; by upward displacement of air.

Question 3.
Give one example of a reaction between the above two gases which produces a solid.
Answer:
NH₃ (g) + HCl (g) → NH₄ Cl (s-solid)

Question 4.
Write equations for the reaction of dil. HCl with each of the following :

1. iron
2. sodium hydrogen carbonate
3. iron [II] sulphide
4. sodium sulphite

Answer:

2008

Question 1.
What property of hydrogen chloride is demonstrated when it is collected by downward delivery (upward displacement)? Why is hydrogen chloride not collected over water.
Answer:
Hydrogen chloride is heavier than air.
Hydrogen chloride cannot be collected over water because hydrogen chloride is highly soluble in water.

Question 2.
Write the equations for the following reactions :

1. dil. HCl and sodium thiosulphate.
2. dil. HCl and lead nitrate solution.

Answer:

2009

Question 1.
Name the gas evolved (formula is not acceptable). The gas produced by the action of concentrated sulphuric acid on sodium chloride.
Answer:
Hydrogen chloride (HCl)

Question 2.
Match each substance A to E listed below with the appropriate description given below :
(A) Sulphur
(B) Silver chloride
(C) Hydrogen chloride
(D) Copper (II) sulphate
(E) Graphite.
(i) A Covalent compound which behaves like an ionic compound in aqueous solution.
(ii) A compound which is insoluble in cold water but soluble in excess of ammonia solution.
Answer:

1. (C) Hydrogen chloride
2. (B) Silver chloride

Question 3.
Write a fully balanced equation for each of the following :

1. Red lead is warmed with concentrated hydrochloric acid.
2. Magnesium metal is treated with dilute hydrochloric acid.

Answer:

Question 4.
Correct the following statements.
HCl is prepared in the laboratory by passing hydrogen chloride directly through water.
Answer:
Hydrochloric acid is prepared in the laboratory by passing hydrogen chloride gas through inverted funnel arrangement in water.

2010

Question 1.
Select the correct answer from A, B, C and D.
(i) Aqua regia is a mixture of :
A : Dilute hydrochloric and cone, nitric acid
B : Cone, hydrochloric acid and dilute nitric acid
C : One part of cone, hydrochloric acid 3 parts of cone, nitric acid.
D : 3 parts of Cone, hydrochloric acid and 1 part of cone, nitric acid
Answer:
D : 3 parts of Cone, hydrochloric acid and 1 part of cone, nitric acid

Question 2.
State your observation when :
A glass rod dipped in NH₄OH soln. is brought near an open bottle containing cone. HCl
Answer:
Dense white fumes of – ammonium chloride are formed.

Question 3.

1. State the salt and the acid, used in the laboratory preparation of hydrogen chloride.
2. Give the equation for the preparation.
3. State a method to prove that the gas jar used for collection of HC1 gas is filled with hydrogen chloride?
4. Observing the method of collection of the gas, state what you can tell about the density of hydrogen chloride ?

Answer:

1. Sodium chloride and Sulphuric acid
2. 
3. In order to know that the jar is filled with the gas, bring a glass rod dipped in ammonium hydroxide solution near its mouth. If dense white fumes of ammonium chloride are produced, it indicates that the gas jar is full of HCl gas.
   
4. The method used to collect HCl is “Upward displacement of air”. This clearly indicates that HCl gas is heavier than air.

Question 4.
How would you distinguish between dilute HCl and dilute HNO₃, by addition of only one solution.
Answer:
HCl (dilute)

Question 5.
Name two gases which can be used in the study of the fountain experiment.
State the common property demonstrated by the fountain experiment ?
Answer:

1. Hydrogen chloride gas (HCl)
2. Ammonia (NH₃)
   Solubility of gases is the common property demonstrated by the fountain experiment.

2011

Question 1.
Choose the correct answer from the choices given :
Hydrogen chloride gas being highly soluble in water is dried by :
(A) Anhydrous calcium chloride
(B) Phosphorous pentaoxide
(C) Quick lime
(D) Concentrated sulphuric acid.
Answer:
(D) Concentrated sulphuric acid.

Question 2.
Write balanced equations of dil. HCl with – Calcium bicarbonate.
Answer:

Question 3.
In the laboratory preparation of hydrochloric acid, Hydrogen chloride gas is dissolved in water.
(i) Draw a diagram to show the arrangement used for the absorption of HCl in water.
(ii) State why such an arrangement is necessary? Give two reasons for the same.
(iii) Write balanced chemical equations for the laboratory preparation of HCl gas when the reactants are :

(A) below 200°C
(B) above 200° C

Answer:
(i) Refer to page 335 of this book.
(ii) Two reasons for the use of funnel arrangement are :

(A) Prevents back suction of water into the flask.
(B) Provides a large surface area for the absorption of the gas (HCl).

2012

Question 1.
Rewrite the correct statement with the missing word/s :
Aqua regia contains one part by volume of nitric acid and three parts by volume of hydrochloric acid.
Answer:
Aqua regia contains one part by volume of cone, nitric acid and three parts by volume of cone, hydrochloric acid.

Question 2.
Give reasons : Hydrogen chloride gas cannot be dried over quick lime.
Answer:
Hydrogen chloride is acidic while quick lime is basic, so they react.

Question 3.
Concentrated hydrochloric acid and Potassium permanganate solution.
Answer:

Question 4.
Give balanced equations with conditions, if any, for the following conversions A to D.
A : Sodium Chloride → Hydrogen Chloride
B : Hydrogen Chloride → Iron (II) chloride
C : Hydrogen Chloride → Ammonium chloride
D : Hydrogen Chloride → Lead chloride.
Answer:

2013

Question 1.
Identify the gas evolved when :

1. Potassium sulphite is treated with dilute hydrochloric acid.
2. concentrated hydrochloric acid is made to react with manganese dioxide.

Answer:

1. Sulphur dioxide gas
2. Chlorine gas

Question 2.
State one appropriate observation for

1. Copper sulphide is treated with dilute hydrochloric acid.
2. A few drops of dil. HCl are added to AgNO₃ soln, followed by addition of NH₄OH soln.

Answer:

1. A colourless gas with a smell of rotten eggs is given off and a green coloured solution is formed.
2. White ppt is formed which dissolves in ammonium hydroxide.

2014

Question 1.
Fill in the blanks from the choices in the bracket : Quicklime is not used to dry HCl gas because _____ (CaO is alkaline, CaO is acidic, CaO is neutral)
Answer:
Quicklime is not used to dry HCl gas because CaO is alkaline.

Question 2.
Write the balanced equation for : Action of dilute hydrochloric acid on sodium sulphide.
Answer:
Action of dilute hydrochloric acid on sodium sulphide.
Na₂S + 2HCl → 2NaCl + H₂S

Question 3.
State your observation : Dilute HC1 is added to sodium carbonate crystals.
Answer:
Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂ ↑
effervescence of CO₂ seen which turns lime water milky

Question 4.
Study the figure given below and answer the questions that follow :

1. Identify the gas Y.
2. What property of gas Y does this experiment demonstrate?
3. Name another gas which has the same property and can be demonstrated through this experiment.

Answer:

1. Identify the gas Y — It is HCl (Hydrogen chloride)
2. Property of Y —Highly solubility in water
3. The another gas has same property — NH₃ (Ammonia)

2015

Question 1.
Select from the gases — ammonia, ethane, hydrogen chloride, hydrogen sulphide, ethyne — The gas which produces dense white fumes with ammonia gas.
Answer:
Hydrogen chloride

Question 2.
Identify the acid which on mixing with silver nitrate solution produces a white precipitate which is soluble in excess ammonium hydroxide.
Answer:
Dilute hydrochloric acid

Question 3.
The following questions are pertaining to the laboratory preparation of hydrogen chloride gas:

1. Write the equation for its preparation mentioning the condition required.
2. Name the drying agent used in the above preparation and give a reason for the choice.
3. State a safety precaution you would take during the preparation of hydrochloric acid.

Answer:

1. The equation for the laboratory preparation of hydrogen chloride gas :
   
   Although it is a reversible reaction, it goes to completion as hydrogen chloride continuously escapes as a gas.
   The reaction can occur up to the stage of the formation of sodium sulphate on heating above 200°C.
   
2. The drying agent used in the laboratory preparation of hydrochloric acid is conc.sulphuric acid.
   The other drying agents such as phosphorus pentoxide (P₂O₅) and quick lime
   (CaO) cannot be used because they react with hydrogen chloride.
   
3. A safety precaution which should be taken during the preparation of hydrochloric acid :
   Always wear chemical splash goggles, chemical-resistant gloves and a chemical resistant apron in the laboratory during the preparation of hydrochloric acid.

2016

Question 1.
Select the correct answer from A, B, C and D : The aim of the Fountain experiment is to prove that :
(A) HCl turns blue litmus red
(B) HCl is denser than air
(C) HCl is highly soluble in water
(D) HCl fumes in moist air.
Answer:
(C) HCl is highly soluble in water

Question 2.
Fill in the blank : _____ (AgCl / PbCl₂), a white precipitate is soluble in excess NH₄OH.
Answer:
AgCl (because of formation of diammine silver chloride), a white precipitate is soluble in excess NH4OH.

Question 3.
Write balanced chemical equation for : Action of hydrochloric acid on sodium bicarbonate.
Answer:
NaHCO₃ + HCl → NaCl + H₂O + CO₂ ↑

Question 4.
State your observations when dilute hydrochloric acid is added to :

1. Lead nitrate soln. and the mixture is heated.
2. Copper carbonate.
3. Sodium thiosulphate.

Answer:

When dilute hydrochloric acid is added to lead nitrate white precipitates of lead chloride is formed.

When dilute hydrochloric acid is added to copper carbonate brisk effervescence due to the liberation of carbon dioxide is observed.

When dilute hydrochloric acid is added to sodium thiosulphate pale yellow residue (due to formation of sulphur) is formed and a gas with choking odour is formed.

Question 5.
Identify the gas evolved and give the chemical test in when dilute hydrochloric acid reacts with :

1. Sodium sulphite.
2. Iron (II) sulphide.

Answer:

2017

Question 1.
Fill in the blanks from the choices given – Potassium sulphite on reacting with hydrochloric acid, releases gas. _____ [Cl₂, SO₂, H₂S]
Answer:
Potassium sulphite on reacting with hydrochloric acid, releases SO₂ gas.

Question 2.
Identify the substance underlined – A solid formed by the reaction of two gases, one of which is acidic and the other basic in nature.
Answer:
Ammonium chloride.

Question 3.
State one relevant observation – Action of dilute hydrochloric acid on iron [II] sulphide.
Answer:
A foul smelling gas like rotten eggs is given off.

Question 4.
Certain blanks spaces are left in the following tables as A & 8. Identify each of them.

Answer:
A : The products are sodium hydrogen sulphate (NaHSO₄) and HCl gas.
B : HCl gas as collected by the upward displacement of air.

Q. Complete the statements given below pertaining to hydrogen chloride gas or hydrochloric acid.

1. Hydrogen chloride gas is not dried using _____ (cone.H₂SO₄, CaO).
2. Hydrogen chloride gas on heating above 500°C gives hydrogen and chlorine.
   The reaction is an example of _____ (thermal decomposition, thermal dissociation).
3. Iron reacts with hydrogen chloride gas forming [iron (II) chloride, iron (III) chloride) and hydrogen. The reaction is an example of _____ (double decomposition, synthesis, simple displacement).
4. Hydrogen chloride and water are examples of (polar covalent compounds, non-polar covalent compounds) and a solution of hydrogen chloride in water _____ (contains, does not contain) free ions.
5. Addition of _____ (sodium nitrate, zinc nitrate, silver nitrate) to hydrochloric acid, gives an insoluble precipitate of the respective chloride. This precipitate is _____ (soluble,insoluble) in ammonium hydroxide and _____ (soluble, insoluble) in dilute taitric add.
6. Addition of _____ [iron (III) sulphide, iron (II) sulphide, iron pyrites] to dilute hydrochloric acid results in liberation of hydrogen sulphide gas.
7. Aqua regia is a mixture of _____ (one, two, three) part/s of concentrated nitric acid and )_____ (one, two, three) part/s of concentrated hydrochloric acid by _____ (weight, volume). In aqua regia, nitric acid _____ (oxidises, reduces) hydrochloric acid to chlorine.
8. Hydrochloric acid can be converted into chlorine by heating with _____ [calcium oxide, lead (H) oxide, lead (IV) oxide] which acts as a / an _____ (oxidising, reducing) agent.

Answer:

1. CaO
2. Thermal dissociation
3. Iron (II) chloride ; simple displacement
4. polar covalent compounds ; contains
5. silver nitrate ; soluble ; insoluble
6. iron (II) sulphide
7. one, three, volume, oxidises
8. Lead (II) oxide ; oxidisirig.

Additional Questions

Question 1.
Give a reason why
(a) gastric juices of luammals are acidic
(b) HCl is considered a polar covalent compound.
Answer:
(a) HCI gas occurs in free state in gastric juices of mammals.
(b) Due to difference in electronegativities of H and Cl ; The bond in HCl is a polar covalent.

Question 2.
Give the equation for preparation of HCI gas by Synthesis. State two conditions involved in the synthesis.
Answer:

Question 3.
Give a balanced equation for preparation of HCl gas in the laboratory from sodium chloride.
Answer:

Question 4.
In the laboratory preparation of HCl frem sodium chloride, state why the following are preferred –

1. Cone. H₂SO₄ as a reactant
2. Temp, below 200°C
3. Cone. H₂SO₄ as a drying agent.

Answer:

1. Since it is non-volatile and has a high boiling point.
2. The glass apparatus does not crack, no hard crust is formed, fuel is not wasted.
3. It only removes moisture content of the gas but not react with it.

Question 5.
State with reasons the method of collection of HCl gas in the laboratory.
Answer:
HCl gas is collected by upward displacement of air because it is 1.28 times heavier than air. It is not collected in water because it is highly soluble in water.

Question 6.
Compare the density of HCl gas with air and state the solubility of HCl gas in water.
Answer:
V.D of HCl = 18.25, V.D of air = 14.4. It is highly soluble in water.

Question 7.
State why HCl gas forms a mist of droplets of HCl acid in moist air.
Answer:
Due to high solubility, HCl gas fumes in moist air and forms a mist of droplets of HCl acid.

Question 8.
State what the fountain experiment demonstrates with reference to HCl gas.
Answer:
Fountain experiment demonstrates the solubility of HCI gas in water and its acidic nature.

Question 9.
State the colour change in three different indicators in presence of HCl gas.
Answer:

Question 10.
Give a balanced equation for the thermal dissociation of

1. a gas
2. a solid (both containing the chloride ion).

Answer:

Question 11.
Give the equation and state the observation seen when HCl gas reacts with ammonia.
Answer:
When a gas jar containing hydrogen chloride gas is inverted over ajar full of ammonia gas, dense white fumes are formed.

Question 12.
Convert iron to iron (II) chloride using HCl gas.
Answer:

Question 13.
Explain the arrangement (i) not used (ii) used – for converting HCl gas into HCl acid.
Answer:
Hydrochloric acid is prepared by dissolving hydrogen chloride gas in water usi ig a special funnel arrangement.

1. Direct absorption of HCl gas in water using a delivery tube i.e., arrangement (i) causes back suction.
Hydrogen chloride gas is extremely soluble in water. If a delivery tube through which HCl gas is passed is directly immersed in water, the rate of absorption of HCl gas is high and hence a partial vacuum is created in the tube. The pressure outside being higher causes the water to be pushed up into the delivery tube and damages the apparatus. This is called back-suction.
2. Special funnel arrangement, i.e., arrangement (ii) is used for avoiding back suction.
The funnel arrangement :

(a) Prevents or minimizes back-suction of water.
(b) Provides a large surface area for absorption of HCl gas.

The rim of the funnel is placed so that it just touches the trough containing water. If back-suction occurs, the water rises up the funnel and the level outside the funnel falls, thus creating an air gap between the rim of the funnel and the surface of water. The pressure outside and inside equalize and the water which had risen in the funnel falls down again. This process continues till the water in the trough is saturated with hydrogen chloride gas resulting information of hydrochloric acid.
Hence hydrochloric acid is not prepared in the laboratory by passing hydrogen chloride gas directly through water, but prepared using a special funnel arrangement.

Question 14.
Explain the term ‘constant boiling mixture’.
Answer:
A solution of HCl in water forms a constant boiling mixture with water.

Question 15.
State why dilute HCl cannot be concentrated beyond a certain concentration by boiling.
Answer:
On boiling the mixture evolves out the vapours of both acid and water in the same proportion as in the liquid. Hence dil HCl cannot be concentrated beyond a certain concentration.

Question 16.
Name the ions obtained when HCl dissociates in aqueous solution.
Answer:
Hydronium ions.

Question 17.
Name the ion responsible for acidic nature of HCl acid.
Answer:
The presence of hydrogen ions |H+| imparts acidic nature to HCl.

Question 18.
State which of two – a solution of HCl in water or in toluene is an electrolyte, giving reasons.
Answer:
A solution of hydrogen chloride in water; water being a covalent solvent ionizes aqueous solution of HCl shows acidic properties and is an electrolyte, whereas toluene is not; being not a polar solvent.

Question 19.
Give four different word equations relating to acidic properties of an aq. soln. of HCl gas.
Answer:
Zinc + Hydrochloric acid → Zinc chloride + Hydrogen
Sodium hydroxide + Hydrochloric acid → Sodium chloride + Water
Sodium carbonate + Hydrochloric acid → Sodium chloride + Carbon dioxide + Water
Calcium oxide + Hydrochloric acid → Calcium chloride + Water

Question 20.
Give balanced equations to obtain

1. H₂
2. CO₂
3. SO₂
4. H₂S from dil. HCl.

Answer:

1. Zn + 2HCl → ZnCl₂ + H₂
2. Na₂CO₂ + 2HCl → 2NaCl + H₂O + CO₂
3. Na₂SO₃ + 2HCl → 2NaCl + H₂0 + SO₂
4. FeS + 2HCl → FeCl₂ + H₂S

Question 21.
Convert two soluble metallic nitrates to insoluble metallic chlorides using dil. HCl.
Answer:

Question 22.
State how you would prove that HCl contains

1. hydrogen – using an active metal below magnesium
2. chlorine – using an oxidising agent not containing lead.

Answer:

Question 23.
State the composition of aqua regia. State which component is the oxidising agent in aqua regia.
Answer:

Question 24.
Convert hydrochloric acid to nascent chlorine.
Answer:

Question 25.
State why aqua regia dissolves gold, which is insoluble in all other acids.
Answer:
In aqua regia (a mixture of 1 part cone. HNO3 and 3 parts cone. HCl by volume), nitric acid oxidises hydrochloric acid to give nascent chlorine. This nascent chlorine is very reactive. It reacts with gold to give gold (III) chloride, which is soluble in water.

Question 26.
Give three tests for hydrochloric acid. Convert silver nitrate to a soluble salt of silver using hydrochloric acid and an alkali.
Answer:

1. If glass rod dipped in ammonia soln. (NH₄OH) brought near vapours of hydrochloric acid.
   Dense white fumes of – ammonium chloride are formed.
2. Addition of silver nitrate soln. to dil. HCl (acidified with dil. HNO₃)
   Curdly white precipitate – of silver chloride obtained.
   
3. Action of heat on a mixture of manganes dioxide and cone. HCl Greenish yellow gas (chlorine).

Question 27.
State two industrial products manufactured from hydrochloric acid, which are also manufactured from nitric and sulphuric acid. Give two general uses of hydrochloric acid.
Answer:
Industrial products manufactured from HCl acid are : Dyes, paints, drugs.
General uses of hydrochloric acid are :

1. Hydrochloric acid dissolves the calcium phosphate present in bones.
2. Hydrochloric acid dissolves the metallic oxides coating on the surface of metals. Thereby cleans the metallic surface.

Unit Test Paper 7A — Hydrogen Chloride

Q.1. Give balanced equations for the conversions A, B, C, D and E given below :

Answer:

Q.2. Give reasons for the following :

Question 1.
In the laboratory preparation of HCl acid from NaCl and cone. H₂SO₄, the residual salt formed at temperatures above 200°C forms a hard crust and sticks
to the glass.
Answer:
When sodium chloride and cone, sulphuric acid is heated above 200°C ; sodium sulphate forms a hard crust, sticks to the glass and is difficult to remove.

Question 2.
Dense white fumes are obtained when a jar of HCl gas is inverted over a jar of ammonia gas.
Answer:
When a gas jar containing hydrogen chloride gas is inverted over of jar full of ammonia gas dense white fumes are formed. These fumes consists of particles of solid ammonium chloride suspended in air.

Question 3.
In the fountain experiment to demonstrated the high solubility of HCl gas in water, dry HCl gas is filled in the round bottom flask.
Answer:
HCl gas present in the flask dissolves in water due to high solubility, creating a partial vacuum in the flask. The outside pressure being higher pushes the water up the jet tube which emerges as fountain.

Question 4.
Iron sheets are cleaned with hydrochloric acid before dipping into molten zinc for galvanizing.
Answer:
Hydrochloric acid dissolves the metallic oxide coating on the surface of the metal, thereby cleans the metallic surface.

Question 5.
Hydrogen chloride gas fumes in moist air but hydrogen sulphide gas does not.
Answer:
HCl gas fumes in moist air due to its high solubility and forms a mist of droplets of HCl acid while H₂S does not.

Q.3. Complete the statements given below using the correct word/s

1. An aqueous solution of HCl gas is named _____ (aqua fortis/muriatic acid/oil of vitriol)
2. The salt obtained when rock salt reacts with cone. H₂SO₄ at temperatures below 200°C is a/an _____ (acid/normal) salt.
3. In the preparation of HCl acid from HCl gas, a funnel arrangement provides _____ (less/more) surface area for absorption of the gas.
4. The ions which impart acidic properties to an aqueous solution of hydrogen chloride are _____ (chloride/hydrogen/hydronium)
5. The indicator which does not change colour on passage of hydrogen chloride gas is _____ (moist blue litmus/phenolphthalein/methyl orange)

Answer:

1. mutriatic acid
2. normal
3. more
4. hydrogen
5. phenolphthalein

Q.4. Choose from the letters A, B, C, D and E, to match the descriptions 1 to 5 given below.
A : NH₄ Cl
B : AgCl
C : PbCl₂
D : FeCl2
E : Ag(NH₃)₂ Cl

1. A solubl salt obtained on reaction of a metallic chloride with liquor ammonia.
2. A salt which is insoluble in dilute nitric acid but soluble in ammonium hydroxide.
3. A salt obtained on reaction of an active metal with hydrogen chloride gas.
4. A salt obtained when a basic gas reacts with hydrogen chloride gas.
5. A salt soluble in hot water but not in cold, obtained on heating an oxidising agent with cone. HCl.

Answer:

1. E [Ag (NH₃)₂ Cl]
2. B (AgCl)
3. D (FeCl₂)
4. A (NH₄Cl)
5. C (PbCl₂)

Q.5. Select the correct word or formula from the same given in bracket :

1. The substance reacted with cone. HCl and heated to prove that cone. HCl contains Cl₂. (PbCl₂/PbO₂/Pb0)
2. The metal reacted with dil. HCl to prove that dil. HCl contains hydrogen. (Cu/Fe/Ag/Pb)
3. The gas/es which is / are heavier than air and highly soluble in water. (NH₃ / HCl/CO₂/H₂S)
4. The acid which is not an oxidising agent. (Cone. HNO₃/ Cone. HCl/Conc. H₂SO₄)
5. The acid which is not a monobasic acid. (Acetic/ Sulphurous/Hydrochloric/Nitric/Formic acid)

Answer:
1. PbO₂
2. Fe
3. HCl(g)
4. Cone. HNO₃
5. Sulphurous acid

Q.6. Select the correct words from the list given below to complete the following word equations :
Metallic oxide, active metal, metallic carbonate, metallic bisulphite, active metal, metallic hydroxide, metallic bicarbonate, metallic sulphate, metallic sulphide.

1. _____ + hydrochloric acid (dil) → salt + hydrogen
2. _____ + hydrochloric acid (dil) → salt + water
3. _____ + hydrochloric acid (dil) → salt + water + carbon dioxide
4. _____ + hydrochloric acid (dil) → salt + water + sulphur dioxide
5. _____ + hydrochloric acid (dil) → salt + hydrogen sulphide

Answer:

1. active metal
2. metallic hydroxide
3. metallic carbonate / bicarbonate
4. metallic sulphite
5. metallic sulphide

For More Resources

New Simplified Chemistry Class 10 ICSE Solutions – Metallurgy

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

Viraf J Dalal Chemistry Class 10 Solutions and Answers

Simplified ChemistryEnglishMathsPhysicsChemistryBiology

For Objective and ICSE Board Type Questions Questions (Solved)

2002

Question 1.
Match the metals/alloys – brass, with its correct use.
Uses : (a) steel making (b) aeroplane wings (c) galvanizing (d) radiation shield (e) electrical fittings
Answer:

Question 2.
In order to obtain aluminium, the following inputs are required : Bauxite, sodium hydroxide and graphite. The aluminium compound in bauxite is aluminium oxide and the main impurity is iron (III) oxide. Aluminium is obtained by the electrolysis of aluminium oxide dissolved in cryolite,

1. When bauxite is treated with sodium hydroxide solution what happens to the : (a) aluminium oxide (b) iron (c) oxide.
2. Name the process used for the purification of bauxite.
3. Write the equation for the action of heat on aluminium hydroxide
4. Write the formula of cryolite.

Answer:
(i) (a) Aluminium oxide reacts with NaOH (aq.) at 150-200°C to give sodium aluminate which is soluble in water.
(b) Iron (II) oxide remains unaffected.
(ii) Baeyer’s method is used for removal of impurities.

Aluminium hydroxide write below Al₂O₃
(iv) Formula of cryolite – (Na₃ Al F₆)

Question 3.
Write down the word which correctly completes the following sentence : “By dissolving aluminium oxide in cryolite a __ [conducting / non-conducting] solution is produced.
State why is so much graphite is requires for this electrolytic process.
Write the equation for the reaction which takes place at the cathode.
Answer:
“By dissolving aluminium oxide in cryolite a conducting solution is produced.
The graphite anodes are periodically replaced during electrolysis process of fused alumina.
At cathode : 2Al³⁺ + 6e^– → 2Al

Question 4.
In construction work, state why the alloy duralumin is used rather than pure aluminium.
Answer:
Duralumin is light, strong and corrosion resistant.

2003

Question 1.
Name an alloy of copper and zinc.
Answer:
Brass

2004

Question 1.
Element X is a metal with a valency 2. Element Y is a nonmetal with a valency 3.
Write equations to show how X and Y form ions.
Answer:
Y + 3e^– → Y3^– (cations formed)

Question 2.
Cations are formed by _____ (loss / gain) of electrons and anions are formed by _____ (loss / gain) of electrons.
Answer:
Cations are formed by loss of electrons and anions are formed by gain of electrons.

Question 3.
(i) Write three balanced equations for the purification of bauxite by Hall’s process in extraction of Al.
(ii) Name a chemical used for dissolving Al₂O₃. In which state of subdivision is the chemical used.
(iii) Write an equation for the reaction at the anode during the extraction of aluminium by the electrolytic process.
(iv) Mention one reason for the use of aluminium in thermite welding.
Answer:

2005

Question 1.
A to F below relate to the source and extraction of either Zinc or Aluminium. A : Bauxite, B : Coke, C : Cryolite, D : Froth floatation, E : Sodium hydroxide solution, F : Zinc blende.

1. Write down the three letters each from the above list which are relevant to – Aluminium.
2. Fill in the blanks using the most appropriate words from A to F : (a) The ore from which aluminium is extracted must first be treated with so that pure Aluminium oxide can be obtained. (b) Pure Aluminium oxide is dissolved in to make a conducting solution
3. Write the formula of Cryolite.

Answer:

1. Aluminium: Bauxite (A), Cryolite (C), Sodium hydroxide solution (F).
2. (a) Sodium Hydroxide Solution (b) Cryolite
3. Na₃AlF₆

Question 2.
Calcium, Copper, Lead, Aluminium, Zinc, Chromium, Magnesium, Iron.
Choose the major metals from the list given above to make the following alloys :

1. Stainless steel
2. Brass.

Answer:

1. Iron, Chromium
2. Copper, Zinc

2006

Question 1.
Name the following :

1. A metal which is liquid at room temperature.
2. A compound added to lower the fusion temp, of the electrolytic bath in the extraction of Al.
3. The process of heating an ore to a high temperature in the presence of air.

Answer:

1. Mercury or Gallium
2. Cryolite [Na₃ (AlF₆)]
3. Roasting

Question 2.
A strip of copper is placed in four different colourless salt solutions. They are KNO₃, AgNO₃, Zn(NO₃)₂, Ca(NO₃)₂.
Which one of the solutions will finaky turn blue.
Answer:
Silver Nitrate (AgNO₃)

Question 3.
When a metal atom becomes an ion
A : it loses electrons and is oxidized
B : it gains electrons and is reduced
C : it gains electrons and is oxidized
D : it loses electrons and is reduced
(Choose the correct answer from the choices A, B, C and D)
Answer:
A : it loses electrons and is oxidized

2007

Question 1.
In the extraction of aluminium :

1. Which soln. is used to react with bauxite as a first step in obtaining pure aluminium oxide.
2. The aluminium oxide for the electrolytic extraction of aluminium is obtained by heating aluminium hydroxide. Write the equation for this reaction.
3. Name the element which serves as the anode and cathode in the extraction of aluminium.
4. Write the equation for the reaction that occurs at the cathode during the extraction of aluminium by electrolysis.
5. Give the equation for the reaction at the anode when aluminium is purified by electrolysis.

Answer:

2008

Question 1.
Brass is an alloy of :
A. Copper and tin
B. Copper and zinc
C. Zinc and lead
D. Lead and tin
Answer:
B. Copper and zinc

Question 2.
The following is a sketch of an electrolytic cell used in the extraction of aluminium :

1. What is the substance of which the electrodes A and B are made?
2. At which electrode (A or B) is the aluminium formed ?
3. What are the two aluminium compounds in the electrolyte C ?
4. Why is it necessary for electrode B to be continuously replaced ?

Answer:

1. Electrodes A and B are made of graphite. Electrode B is carbon (graphite) lining while, electrode A is thick rods of graphite.
2. Aluminium is formed at cathode in the molten state which can be taken out through a tapping hole.
3. The two aluminium compounds in the electrolyte C are Alumina (Al₂O₃) and Cryolite (Na₃AlF₆).
4. This is because electrode (B i.e. anode) is oxidised by the oxygen produced to carbon monoxide.

2009

Question 1.
The metal oxide which can react with acid as well as alkali is :
A. Silver oxide
B. Copper (II) oxide
C. Aluminium oxide
D. Calcium oxide
Answer:
C. Aluminium oxide

Question 2.
Correct the following statements. — Haematite is the chief ore of aluminium.
Answer:
Haematite is the chief ore of iron.
Or
Bauxite is the chief ore of aluminium.

Question 3.
The sketch below illustrates the refining of aluminium by Hoope’s process.

1. Which of A and B is the cathode and which one is the anode ?
2. What is the electrolyte in the tank?
3. What material is used for the cathode ?

Answer:

1. A are graphite rods and they act as cathode, B act as anode.
2. Molten Fluorides.
3. Graphite rods dipped in pure molten aluminium.

Question 4.
State the property of the metal being utilized in the following :

1. Zinc in Galvanization
2. Aluminium in Thermite welding

Answer:
Use of metal :

(a) Zinc in Galvanization
(b) Aluminium in Thermite welding

Property :

(a) Zinc forms a protective layer of zinc oxide which prevents rusting of iron.
(b) Strong affinity for oxygen.

2010

Question 1.
State the main constituent metal in each alloy :

1. Duralumin
2. Brass
3. Stainless steel

Answer:

1. Aluminium
2. Copper
3. Iron

Question 2.
Select the correct answer from A, B, C and D – The property which is true for metals.
A : Metals are good conductors of electricity
B : Metals are malleable and ductile
C : Non-polar covalent compounds are formed from metals.
D : Metals have 1, 2 or 3 valence electrons.
Answer:
C : Non-polar covalent compounds are formed from metals.

2011

Question 1.
Choose from the following list of the substances, Acetylence gas, aqua fortis, coke, brass, barium chloride, bronze, platinum.
The substance which is an alloy of zinc, copper and tin.
Answer:
Bronze

Question 2.

(i) Name a metal which is found abundantly in the earth’s crust.
Answer:
Aluminium

(ii) Difference between calcination and roasting?
Answer:
Roasting :

1. Ore is heated in the presence of air.
2. Used generally for sulphide ores. SO₂ gas is given off.
   2ZnS+ 3O₂ → 2ZnO + 2SO₂
3. Volatile impurities are removed as oxides.

Calcination :

1. Ore is heated in the absence of air.
2. Hence Used generally for carbonate ores.
   Hence, CO₂ gas is given off. ZnCO₃ → ZnO + CO₂.
3. Moisture, organic impurities and volatile impurities are removed.

(iii) Name the process used for the enrichment of sulphide ore.
Answer:
Froth floatation process

(iv) Write the chemical formulae of one main ore – of iron and aluminium.
Answer:

• Iron : Haematite → Fe₂O₃
• Aluminium : Bauxite → Al₂,O₃.2H₂O

(v) Write the constituents of electrolyte for – the extraction of aluminium.
Answer:

1. Fused Alumina (Al₂O₃) 1 part by weight.
2. Cryolite fused (Na₃ AlF₆) 3 part by weight.
3. Fluorspar (CaF₂) 1 part by weight.

2012

Question 1.
Choose the correct answer from the options given below

(i) An alkaline earth metal.
(A) Potassium
(B) Calcium
(C) Lead
(D) Copper
Answer:
(B) Calcium

(ii) Which of the following metallic oxides cannot be reduced by normal reducing agents ?
(A) Magnesium oxide
(B) Copper(II) oxide
(C) Zinc oxide
(D) Iron(III) oxide
Answer:
(A) Magnesium oxide

Question 2.
Match the properties and uses of alloys in List 1 with the appropriate answer from List 2.

Answer:

1. (B) Brass
2. (A) Duralumin
3. (D) Stainless stell
4. (E) Solder
5. (C) Bronze

Question 3.
Name the following metals :

1. A metal present in cryolite other than sodium.
2. A metal which is unaffected by dilute or concentrated acids.

Answer:

1. Aluminium
2. Platinum

Question 4.
The following questions are relevant to the extraction of Aluminium :

1. State the reason for addition of caustic alkali to bauxite ore during purification of bauxite.
2. Give a balanced chemical equation for the above reaction.
3. Along with cryolite and alumina, another substance is added to the electrolyte mixture. Name the substance and give one reason for the addition.

Answer:

1. The caustic alkali dissolves aluminium oxide to form sodium aluminate.
2. 
3. Fluorspar is added. It helps in increasing the conductivity of the mixtures.

2013

Question 1.
The amphoteric metallic oxide is
(A) Calcium oxide
(B) Barium oxide
(C) Zinc oxide
(D) Copper (II) oxide
Answer:
(C) Zinc oxide is an amphoteric oxide

Question 2.
The metals zinc and tin are present in the alloy :
(A) Solder
(B) Brass
(C) Bronze
(D) Duralumin.
Answer:
(C) Bronze

Question 3.
Using the information below about X and Y – complete the following questions :

1. ____ is the metallic element.
2. Metal atoms tend to have a maximum of _____ electrons in the outermost energy level.
3. Non-metallic elements tend to form _____ oxides while metals tend to form _____ oxides.
4. Non-metallic elements tend to be _____ conductors of beat and electricity.
5. Metals tend to _____ electrons and act as _____ agents in their reactions with elements and compounds,

Answer:

1. Y is the metallic element.
2. Metal atoms tend to have a maximum of three electrons in the outermost energy level.
3. Non-metallic elements tend to form acidic oxides while metals tend to form basic oxides.
4. Non-metallic elements tend to be bad conductors of heat and electricity.
5. Metals tend to lose electrons and act as reducing agents in their reactions with elements and compounds.

Question 4.
The following questions relate to the extraction of aluminium by electrolysis :

(i) Name the other aluminium containing compound added to alumina and state its significance,
Answer:
The compound is cryolite [Na₃AlF₆]
The addition of cryolite lowers the melting point of alumina from 2050°C to 660 °C.
Furthermore, it increases the electrical conductivity of the molten alumina.

(ii) Give the equation for the reaction that takes place at the cathode.
Answer:
Al³⁺ + 3e^– → Al

(iii) Explain why is it necessary to renew the anode periodically.
Answer:
The anode (which is made of carbon) is attacked by nascent oxygen formed due to the discharge of O^2- ions and changes to carbon dioxide. As the anode is gradually consumed, it is periodically renewed.

2014

Question 1.
Choose the correct answer from the choices :

(i) Heating an ore in a limited supply of air or in the absence of air at a temperature just below its melting point is known as :
(A) smelting
(B) ore dressing
(C) calcination
(D) bessemerisation
Answer:
(C) calcination

(ii) Aluminium powder is used in thermite welding because,
(A) it is a strong reducing agent
(B) it is a strong oxidising agent
(C) it is corrosion resistant
(D) it is a good conductor of heat.
Answer:
(A) it is a strong reducing agent

(iii) The main ore used for the extraction of iron is :
(A) Haematite
(B) Calamine
(C) Bauxite
(D) Cryolite
Answer:
(A) Haematite

Question 2.
State the main components of the following alloys :

1. Brass
2. Duralumin
3. Bronze.

Answer:

Question 3.
Name the following :

1. The property possessed by metals by which they can be beaten into sheets.
2. A compound added to lower the fusion temperature of electrolytic bath in the extraction of aluminium.
3. The ore of zinc containing its sulphide.

Answer:

1. Melleability
2. Cryolite (Na3AlF6)
3. The ore of zinc containing sulphide ZnS (Zinc Blende).

2015

Question 1.
Select which is not an alloy of copper :
(A) Brass
(B) Bronze
(C) Solder
(D) Duralumin.
Answer:
(C) Solder
Solder is an alloy of lead and tin.

Question 2.
Give scientific reasons for : Zinc oxide can be reduced to zinc by using carbon monoxide, but aluminium oxide can – not be reduced by a reducing agent.
Answer:
Zinc ion is lower in electrochemical series. Thus, carbon monoxide provides enough energy and hence reduces zinc oxide to zinc. Aluminium ion is higher in electrochemical series. The carbon monoxide does not produce enough energy and hence aluminium oxide is not reduced to aluminium.

Question 3.
From the list of oxides — SO₂, SiO₂, Al₂O₃, MgO, CO, Na₂O — Select

1. A basic oxide
2. An amphoteric oxide.

Answer:

1. Na₂O
2. Al₂O₃

Question 4.
A metal ‘X’ has a valency 2 and a non-metal ‘Y’ has a valency 3. Write an equation to show how ‘Y’ forms an ion.
Answer:

Question 5.
(i) Describe the role played in the extraction of aluminium by each of the substances listed.

(a) Cryolite
(b) Sodium hydroxide
(c) Graphite

(ii) Explain why :

(a) In the electrolysis of alumina using the Hall Heroult’s Process the electrolyte is covered with powdered coke.
(b) During galvanization, iron sheets are coated with zinc during galvanization.

Answer:
(i)

(a) Cryolite lowers the melting point of alumina from 2050° to 950°C. This in turn increases the conductivity of electrolyte and saves on electricity, which is the main source of energy in the reduction of alumina.
(b) Sodium hydroxide dissolves the alumina (Al₂O₃), but not the impurities to form sodium aluminate. The impurities are filtered out and the sodium aluminate is treated with carbon dioxide to form pure aluminium hydroxide. Alumina is recovered from sodium hydroxide by strong heating.
(c) Graphite is used as cathode as it is a good conductor of electricity and is not attacked by the chemicals.

(ii)

(a) It prevents burning of carbon anodes and prevents heat loss from the molten electrolyte.
(b) Zinc forms a protecting coating on the surface of iron and hence prevents it from rusting. Zinc by itself form a protective layer of zinc oxide and hence does not tarnish.

Question 6.
Select from the following salts — AgCl, MgCl₂, NaHSO₄, PbCO₃, ZnCO₃, KNO₃, Ca(NO₃)₂ — the salt which on heating gives a yellow residue when hot and white when cold.
Answer:
On heating, this salt gives a yellow residue when hot and a white residue when cold is ZnCO₃

2016

Question 1.
Fill in the blanks from the choices given :
Metals are good _____ (oxidizing agents/reducing agents)
because they are electron _____ (acceptors / donors).
Answer:
Metals are good reducing agents because they are electron donors.

Question 2.
Select the correct answer from A, B, C and D :kThe two main metals in Bronze are :
(A) Copper and zinc
(B) Copper and lead
(C) Copper and nickel
(D) Copper and tin
Answer:
(D) Copper and tin

Question 3.
Identify the term in the following :
“The method used to separate ore from gangue by preferential wetting.”
Answer:
Froth flotation process

Question 4.

1. Name the solution used to react with Bauxite-as a first step in obtaining pure aluminium oxide, in the Baeyer’s process.
2. Write the equation for the reaction where the – aluminum oxide for the electrolytic extraction of aluminum is obtained by heating aluminum hydroxide.
3. Name the compound added to – pure alumina to lower the fusion temperature during the electrolytic reduction of alumina.
4. Write the equation for – the reaction that occurs at the cathode during the extraction of aluminium by electrolysis.
5. Explain why – it is preferable to use a number of graphite electrodes as anode instead of a single electrode, during the abvoe electrolysis.

Answer:

1. Sodium hydroxide.
2. 
3. Cryolite (Na₃Al F₆) acts as a solvent and lower the fusion temperature from 2050°C to 950°C.
4. Cathode : (rich in electron)
   AL³ + 3e^– → Al
5. It is preferable to use a number of graphite electrodes as anode because anode gets oxidised by the oxygen evolved.
   Hence, if large number of electrodes are used it will keep the process continuous for a longer time.

2017

Question 1.
From the list of terms given, choose the most appropriate term to match the given description: [calcination, roasting, pulverisation, smelting]

1. Crushing of the ore into a fine powder.
2. Heating of the ore in the absence of air to a high temperature.

Answer:

1. Pulverisation
2. Calcination

Question 2.
Name the following :

1. An alloy of lead and tin that is used in electrical circuits.
2. An ore of zinc containing its sulphide.
3. A metal oxide that can be reduced by hydrogen.

Answer:

1. Fusible alloy
2. Zincite (ZnS)
3. Copper oxide (CuO)

Question 3.
Answer the following questions with respect to the electrolytic process – in the extraction of aluminium.

1. Identify the components of the electrolyte other than pure alumina and the role played by each.
2. Explain why powdered coke is sprinkled over the electrolytic mixture.

Answer:

1. Cryolite (Na₃AlF₄) : It increases the conductivity of mixture and lowers the m.p. of electrolyte from 2050°C to 950°C.
2. Fluorspar (CaF₂) : It increases mobility of ions in the mixture as it acts as solvent for alumina and cryolite.
   Powdered coke prevents (a) heat loss from the electrolyte (b) burning of electrodes projecting out of electrolyte.

Question 4.
Complete the following by selecting the correct option from the choices given –

1. The metal whose oxide, which is amphoteric, is reduced to metal by carbon reduction _____ [Fe / Mg / Pb / Al]
2. The divalent metal whose oxide is reduced to metal by electrolysis of its fused salt is _____ [Al / Na / Mg / K]

Answer:

1. The metal whose oxide, which is amphoteric, is reduced to metal by carbon reduction Pb (Lead).
2. The divalent metal whose oxide is reduced to metal by electrolysis of its fused salt is Mg (Magnesium).

Additional Questions

Question 1.
State how the physical and chemical property differences between metals and non-metals are related to their basic atomic structure.
Define a metal with particular emphasis on (i) ionization (ii) valency (iii) formation of oxides.
State the position [group] in the periodic table to which the following metals belong (i) Na – alkali metal (ii) Mg – alkaline earth metal (iii) Fe and Zn transition elements (iv) inner transition elements (metals) (v) Al – post transition element.
Answer:
Atoms of Metallic elements, in general, have relatively larger atomic size. Hence, their valence electrons are held less tightly by the nucleus. As such, the valence electrons are mobile, leading to good electrical and thermal conductivity in case of metals. Further, with 1,2 or 3 valence electrons, metals can easily lose electrons to form cations. Thus, metal are electropositive in nature and are strong reducing agents.
On the other hand, non-metallic elements, in general, have relatively smaller atomic size. Hence their valence electrons are held tightly by the nucleus. As such their valence electrons are not mobile, thus making non-metals bad conductor of heat and electricity. Further, non-metals have 5, 6 or 7 valence electrons. As such, non-metals tend to gain electrons to form anions. Thus non-metals are electronegative in nature and strong oxidising agents.
Thus, we find that the physical and chemical properties of metals and non-metals are related to their basic atomic structure.
Defination of Metals :

1. Atoms of metals with 1, 2 or 3 electrons in their valence shell can easily lose their valence electrons to form cations e.g.
   
2. As metals can easily lose electrons to form cations, metals are electropositive in nature.
3. Metals on reacting with non-metals form ionic or electrovalent compounds, e.g.
   
4. As metals tend to form cations, metals show a positive valency of 1,2 or 3.

Position of Metals in the periodic table :

1. Na – alkali metal – Group I (IA)
2. Mg – alkaline earth metal – Group 2 (IIA)
3. Fe and Zn transition elements – Group 9 (VIII), Group 12 (IIB)
4. Inner transition elements : zero group.
5. Al-post transition element: Group 13 (III A)

Question 2.
Metals occur in the free state and in the combined state, name two metals which occur in the free or native state. In the combined state metals occur in the form of compounds. Name two different metallic compounds in each case which occur as

1. halides
2. oxides
3. sulphides.

Answer:
Gold and Platinum are the two metals that occur in the free or native state.
The metallic compounds which occur in :

1. Halides – Cryolite[Na₃AlF₆], Flurospar[CaF₂], Rock Salt[NaCl]
2. Oxides – Bauxite[Al₂O₃.2H₂O], Zincite[ZnO], Cuprite[Cu₂O]
3. Sulphides – Iron Pyrite[FeS₂], Zinc blende[ZnS], Gdlena[PbS]

Question 3.
Differentiate between

1. mineral & ore
2. matrix & flux.

Answer:
Differentiate between mineral & ore
Mineral :

• The compounds of various metal found in nature associated with their earthly impurities are called minerals.

Ore :

• The naturally occurring minerals from which metals can be extracted profitably and conveniently are called ores,

Differentiate between matrix & flux

1. Matrix : The rocky impurities including silica [SiO₂], mud etc. associated with the ore is called matrix or gangue.
2. Flux : The substance added to the ore to get rid of the matrix resulting in the formation of a fusible compound slag.

Question 4.
Give the (i) common (ii) chemical nadie (iii) formula of two common ores each of aluminium, zinc and iron.
Answer:

Question 5.
In the stages involved in the extraction of metals in general – give reasons for the following.

(i) Dressing of the ore is an essential process in the extraction of metal from its ore.
Answer:
The ores are found mixed with earthy impurities like sand, clay, lime stone etc. These unwanted impurities in the ore are called gangue or matrix.
The process of removal of gangue from powdered ore is called concentration or ore dressing.
Hence, it is the essential process in the extraction of metal from its ore because it convert’s the impure ore to pure concentrated ore

(ii) An electromagnetic wheel is used in the magnetic separation process of ore from gangue.
Answer:
An electromagnetic wheel is used in the magnetic separation process of ore from gangue as it seperate’s the magnetic particles from the non-magnetic particles. The magnetic particles get attracted to the magnetic wheel and thus get seperated from the gangue.

(iii) In the froth floatation process, the ore floats on the top & the gangue settles down.
Answer:
The impurities get wetted by water and remain behind in the tank. Since, the ore is lighter, it comes on the surface with the froth and the impurities(gatlgue) are left behind.

(iv) Magnetic separation is not used during the dressing of bauxite ore in the extraction of aluminium.
Answer:
Bauxite is concentrated by Leaching (Baeyer’s process). The impure bauxite is treated with concentrated NaOH, Al₂O₃ and SiO₂ dissolve, but Fe₂O₃ and other basic materials remain insoluble and are removed by filtration.
Aluminium is highly reactive metal, belonging to the III A group of the periodic table. In nature, aluminium is found in the form of its oxide in its ore.
Hence, Magnetic separation is not used during the dressing of bauxite ore in the extraction of aluminium.

(v) Conversion of concentrated ore to its oxide is an essential step in the extraction of metals from the ore, even then the step is not necessary in the metallurgy of aluminium.
Answer:
Conversion of concentrated ore to its oxide is an essential step in the extraction of metals from the ore, even then the step is not necessary in the metallurgy of aluminium because in metallurgy of aluminium, the ore is already an oxide.

(vi) Roasting of the concentrated ore is carried out in the presence of excess air, while calcination of the concentrated ore in the absence or limited supply of air.
Answer:
Roasting is a process of converting an ore into its oxide by heating strongly in presence of excess air, so that oxygen gets added to form the corresponding oxide. It is done on sulphide ores in order to remove sulphur as sulphur gets escape in the form of gas.

Whereas in carbonates ores, one needs to drive out carbonate and moisture impurities. So, ore is heated to a high temperature in absence of air. This process is called calcination.

(vii) Roasting the ore generally results in evolution of sulphur dioxide gas, while calcination of the ore evolves carbon dioxide gas.
Answer:
Generally, sulphide ores are roasted, so SO₂ is given off.
While carbonate and hydrated ores are calcined, so CO₂ or water vapours are given off.

(viii) Reduction of metallic oxides to metal in the extraction of metals from the ores- is based on the position of the metal in the activity series.
Answer:
The method used to extract a metal from its ore depends on the position of the metal in the reactivity series.

(a) Metals higher up in the series need to be extracted using electricity.
(b) Metals lower in the series can be extracted by reduction with carbon.

(ix) Oxides or halides of highly electropositive metals e.g. K, Na, Ca, Al are reduced to metals by electrolysis and not by reduction with coke.
Answer:
Oxides are highly active metals like potassium, sodium, calcium, magnesium and aluminium have great affinity towards oxygen and so cannot be reduced by coke.

(x) Coke is not preferred as a reducing agent in the reduction of the oxide of mercury to its metal, but is preferred in the reduction of the oxide of zinc to its metal.
Answer:
Coke is not preferred as a reducing agent in the reduction of the oxide of mercury to its metal because metals low in the activity series are very reactive and the oxides of the metals can be reduced to metals by heating in air.
The reducing nature of carbon plays an important role in metallurgy and helps extract metals from their ores.
For example :

Question 6.
In the extraction of aluminium from bauxite, the first step is the dressing of the ore by Baeyer’s process. Give balanced equations for the conversion of impure bauxite to pure alumina using a concentrated solution of NaOH.
Answer:
Bauxite (red) contains Fe₂O₃. and SiO₂ as the main impurities. It is crushed to a powder and is treated with a cone, solution of NaOH at 150-200°C (under pressure) when Al₂O₃ dissolves.

Question 7.
In the electrolytic reduction of pure alumina to pure aluminium – by Hall Herault’s process, give the electrolytic reactions involved in the same, resulting in formation of aluminium at the cathode.
Answer:
Aluminium is obtained from alumina (Al₂O₃) by electrolytic reduction. The electrolytic both consists of a mixture of cryolite (Na₃AlF₆) and fluorspar (CaF₂) and alumina (Al₂O₃)

Question 8.
State the function of

1. NaOH
2. cryolite
3. fluorspar in the metallurgy of aluminium.

Answer:
Functions of :
(i) NaOH : Crushed and powdered bauxite is heated with a cone, solution of NaOH at 150-200°C for 2 hours under pressure. The main impurities present in bauxite (Fe2O3 and SiO2) remain unaffected with cone. NaOH since these are not amphoteric. Bauxite, being amphoteric reacts with the base to form sodium aluminate, which is soluble in water. Thus NaOH helps in the purification of the ore.
(ii) Cryolite :

(a) To increase the mobility of the fused mixture.
(b) To lower the fusion point of the mixture.
(c) To increase the electrical conductivity of the mixture.

(iii) Fluorspar :

(a) To increase the mobility of the fused mixture.
(b) To lower the fusion point of the mixture.

Question 9.
Give reasons for the following – pertaining to Hall Herault’s process.

1. The fusion temperature of the electrolyte has to be lowered before conducting the electrolytic reduction.
2. The constituents of the electrolyte in addition to one part of fused alumina contains three parts of cryolite and one part of fluorspar.
3. A layer of powdered coke sprinkled over the electrolytic mixture, protects the carbon electrodes.
4. It is preferred to use a number of graphite electrodes as anode, instead of a single graphite electrode.

Answer:
(i) The liberated A1 metal [m.p. 660°C] may also tend to volatize out and get wasted. Hence the fusion temperature of the electrolytic mixture has to be – lowered.
(ii) The reasons for addition of mainly cryolite [in a higher ratio] and fluorspar to the electrolytic mixture are :

(a) They lowers the fusion point of the mixture i. e. the mixture fuses [melts] around 950°C instead of 2050°C.
(b) They enhances the mobility of the fused mixture by acting as a solvent for the electrolytic mixture.
Thus cryolite in the molten state of subdivision dissolves aluminium oxide.
(c) Addition of cryolite enhances the conductivity of the mixture.
Since pure alumina is almost a non-conductor of electricity

(iii) The layer of powdered coke is sprinkled over the electrolytic mixture because :

(a) It prevents burning of carbon electrodes in air at the emergence point from the bath.
(b) It minimizes or prevents heat loss by radiation.

(iv) The graphite[carbon] anodes are continously replaced during the electrolysis because :

(a) The oxygen evolved at the anode escapes as a gas or reacts with the carbon anode.
(b) The carbon anode is thus oxidised to carbon monoxide which either bums giving carbon dioxide or escapes out through an outlet.
2C + O₂ → 2CO [2CO + O₂ → 2CO₂]
(c) The carbon anode is hence consumed and renewed periodically after a certain period of usage,

Question 10.
Define — (a) alloy, (b) amalgam
Answer:

• Alloy : An alloy is a homogenous mixture of two or more metals and non-metals, out of which at least one is a metal.
  For example, brass (Zn + Cu), bronze (Cu + Sn), solder (Sn +Pb), stainless steel (Fe + Cr + Ni + C) etc.
• Amalgam : An alloy in which mercury is an essential constituent is called an amalgam.
  For example, Dental amalgam (Hg + Ag + Sn), it is used for filling dental cavities.

Question 11.
State (i) composition (ii) reason for alloying (iii) one use of each of the following alloys.

1. Brass
2. Bronze
3. Duralumin
4. Solder [fuse metal]
5. Stainless steel

Answer:

Unit Test Paper 6 — Metallurgy

Q.1. Loss of electrons from an element ‘X’ is represented by : X – 3e^– → X³⁺ (X → X³⁺ + 3e^–)

1. X is a _____ (metal/non-metal) and will form _____ (electrovalent/covalent) compounds only.
Ans. X is a metal and will form electrovalent compounds only.

2. X³⁺ formed is a _____ (cation / anion) and element ‘X’ has a valency of _____ [+2 /+3 / -3].
Ans. X³⁺ formed is a cation and element ‘X’ has a valency of +3.

3. If X³⁺ combines with oxygen the formula of the product is _____ (X₂O₃ / XO / X₃O₂),
Ans. If X³⁺ combines with oxygen the formula of the product is X₂O₃.

4. If the above product in the _____ (solid/molten) state is electrolysed the ion X³⁺ will get discharged at the _____ (anode / cathode).
Ans. If the above product in the molten state is electrolysed the ion X³⁺ will get discharged at the cathode.

5. The ion X³⁺ _____ (accepts / loses) electrons and gets _____ (oxidised / reduced) to neutral _____ (ions / atoms / molecules).
Ans. The ion X³⁺ loses electrons and gets reduced to neutral atoms.

Q.2. Select the correct answer from the list A, B, C and D given in each statement.

1. The oxide of the metal which reacts with both acids and alkalis- to give salt & water.
A : MgO
B : CuO
C : Al₂O₃
D : K₂O

2. The common name of the ore of iron – whose chemical formula is Fe₃ O₄.
A : Iron pyrites
B : Magnetite
C : Haematite
D : Spathic iron ore

3. The chemical name – of the main ore of aluminium.
A : Aluminium flouride
B : Aluminium oxide
C : Sodium aluminium flouride
D : Hydrated aluminium oxide

4. The process of dressing of the ore which involves separation of ore & gangue – due to preferential wetting.
A : Magnetic separation
B : Hydrolytic method
C : Froth flotation method
D : Chemical method

5. The metallic oxide reduced to metal generally by – thermal decomposition.
A : ZnO
B : MgO
C : HgO
D : Al₂O₃
Answer:

1. C : Al₂O₃
2. B : Magnetite
3. D : Hydrated aluminium oxide
4. C : Froth flotation method
5. C : HgO

Q.3. Name the substance A to E, reacted with each reactant below to give the respective product/s.

Answer:

Q.4. Name the following :

1. A metallic ore converted to its oxide – iron [II] oxide on heating the concentrated ore.
2. A black metallic oxide reduced to metal on heating with coke.
3. The compound which on ignition at elevated temperatures gives pure alumina.
4. The non-metal which forms the anode during electrolytic reduction of fused alumina in Hall Heroult’s process.
5. A metal other than manganese, present in duralumin but not in magnalium.

Answer:

Q.5. Match the properties & uses of alloys in List 1 – with the correct answer from List 2.

Answer:

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