Bases and Salts

Frank ICSE Solutions for Class 10 Chemistry – Study Of Acids, Bases and Salts

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Frank ICSE Solutions for Class 10 Chemistry – Study Of Acids, Bases and Salts

PAGE NO : 62
Solution 1:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 1

Solution 2:

  1. (i) Hydrogen chloride HCl
    (ii) Nitric acid HNO3
  2. (i) Carbonic acid H2CO3
    (ii) Oxalic acid (COOH)2
  3. (i) Sulphuric acid H2SO4
    (ii) Hydrogen chloride HCl
  4. (i) Carbonic acid H2CO3
    (ii) Acetic acid

Solution 3:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 2

Solution 4:

  1. The pH of a solution is defined as the negative logarithm (base 10) of the hydronium ion concentration present in the solution.
    pH =-log10 [H3O+]
  2. The three applications of pH scale are:
    • It is used to determine the acidic or basic nature of the solution.
    • It is used to determine hydronium ion concentration present in the solution.
    • It is used to find out neutrality of the solution.

Solution 5:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 3

Solution 6:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 4

Solution 7:

  1. Base in solution furnishes the ions:
    Hydroxide ion/ oxide ion and a metallic ion.
  2. A weak alkali furnishes the ions:
    Hydroxide ion and metallic ion and molecules of weak alkali./
  3. An acid in a solution furnishes the ions:
    Hydronium / Hydrogen ion and a negative ion.

Solution 8:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 5

PAGE NO : 63
Solution 9:

  1. CaO
  2. NaOH
  3. CuO
  4. Cu[(OH)2]
  5. H2CO3
  6. Ferric hydroxide [Fe (OH)3].
  7. CuO
  8. NH3

Solution 10:
Anhydrous hydrogen chloride is not an acid but its aqueous solution is a strong acid because anhydrous means without water and we know that the property of acidity is shown by a substance only when it is dissolved in water or its aqueous solution is prepared.

Solution 11:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 6

Solution 12:
Strength of an acid measures the ease with which the acid can ionize to produce hydrogen or hydronium ions when dissolved in water. Those acids which can easily ionize to form hydrogen ions are called strong acids while those which can partially ionize to form hydrogen ions are called weak acids.
Strength of an acid depends upon many factors such as:

  1. Molecular structure of the acid
  2. The temperature
  3. Properties of the solvent

Solution 13:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 7

Solution 14:
Solution B with pH value 9 will give pink colour with phenolphthalein.
Concept Insight: Bases give pink colour with phenolphthalein because a base will abstract two protons from phenolphthalein and the resulting phenolphthalein ion provides pink colour to the solution.

Solution 15:
Two indicators for identification of acid are methyl red and Thymol blue.

Solution 16:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 8

Solution 17:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 9

Solution 18:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 10

Solution 19:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 11

Solution 20:

  1. Efflorescence: It is the phenomenon by which hydrated salts on exposure to dry air, lose their water of crystallization and crumble to powder.
  2. Hygroscopy: It is the phenomenon by which substances absorb moisture from air, but only sufficiently so as to become wet.
  3. Water of crystallization: It is the fixed amount of water that is present in a crystal as an integral part of its constitution. Hydrated salts are salts having water of crystallisation.

Solution 21:
Deliquescence is the phenomenon by which certain salts absorb moisture from air, lose their water of crystallization and dissolve in it to form a saturated solution.
The substances which exhibit deliquescence are called deliquescent.
For example Caustic soda NaOH, Caustic potash KOH.

Solution 22:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 12

Solution 23:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 13

Solution 24:

  1. Common salt gets wet during rainy season because the commercially available salt contains impurities, like magnesium chloride, which are deliquescent substances. These absorb moisture from atmosphere and make the table salt wet.
  2. (i)  Na2CO4.10H2O = Washing soda
    (ii) MgSO4.7H2O = Epsom salt
    (iii)CuSO4.5H2O = Blue vitriol
    (iv) ZnSO4.7H2O = White vitriol

PAGE NO : 64
Solution 1996-1:

  1. pH of a solution having pH 7 can be increased by adding a base to it such as NaOH.
  2. pH can be decreased by adding an acid such as HCl to it.
    If a solution changes colour of litmus from red to blue, it shows that its pH is above 7.

Solution 1996-2:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 14

Solution 1996-3:

  1. Zinc sulphate = Zinc and dilute sulphuric acid
  2. Copper sulphate = Copper oxide and dilute sulphuric acid
  3. Sodium sulphate = Sodium carbonate solution and dilute sulphuric acid
  4. Lead sulphate = Lead carbonate and dilute sulphuric acid

Solution 1997-1:
The term acid salt means the salt formed by partial replacement of the hydrogens present in the acid by metallic or ammonium ions.
For example: NaHCO3

Solution 1997-2

  1. pH scale is used to express the acidic or basic nature of solution.
  2. pH of pure water is 7 since it does not have any impurities.
  3. (a) A soluble oxide of A will have pH less than the pH of pure water i.e. below 7.
    (b) A solution of ‘B’ will have more pH than pure water i.e. above 7.

Solution 1997-3:

  1. Water of crystallization: It is the fixed amount of water that is present in a crystal as an integral pat of its constitution. Compounds having water of crystallization are called hydrous salts.
    For example: Sodium carbonate Na2CO3 has 10 molecules of water present as water of crystallization Na2CO3.10H2O
  2. Anhydrous: Hydrous salt on heating lose their water of crystallization, such salts are then called anhydrous.
    For example:Na2CO3.10H2O on losing 10 molecules of water forms Na2CO3

Solution 1997-4:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 15

Solution 1998-1:

  1. Water of cystallization.
  2. White.
  3. Efflorescence.
  4. Sodium chloride.

Solution 1998-2:
Those acids which ionize partially in aqueous solution and thus they contain ions as well as molecules of the acid. Organic acid such as CH3COOH, is a weak acid.

Solution 1998-3:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 16

PAGE NO : 65
Solution 1998-4:
The name and formula of the acid salt which gives sodium ions and sulphate ions in solution is Sodium hydrogen sulphate NaHSO4

Solution 1999-1:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 17

Solution 2000-1:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 18

Solution 2001-1:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 19

PAGE NO : 66
Solution 2002-1:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 20

Solution 2003-1:

  1. Hydronium, positive.
  2. Acid, metal.

Solution 2003-2:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 21

Solution 2004-1:
methods for preparation:

  1. Preparation of copper(II) chloride.
    Action of an acid on an oxide or carbonate
  2. Preparation of iron(III) chloride.
    Direct combination
  3. Preparation of iron (II) chloride.
    Action of an acid on a metal
  4. Preparation of lead (ii) chloride
    Precipitation (double decomposition)
  5. Preparation of sodium chloride
    Neutralization of an alkali by an acid.

Solution 2005-1:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 22

PAGE NO : 67
Solution 2005-2:
Positive, hydroxyl, Salt, Neutralization.

Solution 2005-3:
When neutral litmus solution is added to sodium hydrogen carbonate solution, litmus solution turns red

Solution 2006-1:

  1. From pink to colourless.
  2. From orange to pink.
  3. From colourless to red.

Solution 2007-1:

  1. Hydronium
  2. Hydroxide
  3. Salt
  4. Water
  5. Hydrogen

Solution 2007-2:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 23

Solution 2008-1:

  1. Complex salt.
  2. Alkali.

Solution 2009-1:
Acidified potassium dichromate paper

PAGE NO : 68
Solution 2009-2:

  1. Solution B.
  2. Solution A.
  3. Solution B
  4. Solution of ammonium hydroxide NH4OH is a weak alkali.

Solution 2009-3:
Frank ICSE Solutions for Class 10 Chemistry - Study Of Acids, Bases and Salts 24

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New Simplified Chemistry Class 10 ICSE Solutions – Acids, Bases and Salts

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New Simplified Chemistry Class 10 ICSE Solutions -A: Acids, Bases and Salts

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QUESTIONS

2004

Question 1.
Which of the methods, A, B, C, D or E is generally used for preparing the chlorides listed below from (i) to (v)

(A) Action of an acid on a metal
(B) Action of an acid on an oxide or carbonate
(C) Direct combination
(D) Neutralization of an alkali by an acid
(E) Precipitation (double decomposition)

  1. Copper (II) chloride
  2. Iron (II) chloride
  3. Iron (III) chloride
  4. Lead (II) chloride
  5. Sodium chloride Each method is to be used only once.

Answer:
(1) B (2) A (3) C (4) E (5) D

2005

Question 1.

Match from A to F:
A: Acidic oxide,
B: Alkali,
C: Amphoteric oxide,
D: Basic oxide,
E: Deliquescence,
F: Efflorescence

  1. The property of spontaneously giving up water of crystallization to the atmosphere.
  2. A compound, soluble in water and the only negative ions in the soln. are hydroxide ions

Answer:

  1. F: Efflorescence
  2. B: Alkali

Question 2.

What is observed when, neutral litmus soln. is added to sodium hydrogen carbonate solution.
Answer:
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 1

Question 3.

The preparation of lead sulphate from lead carbonate is a two-step process.                                            (Lead sulphate cannot be prepared by adding dilute sulphuric from lead carbonate.)

  1. What is the first step that is required to prepare lead sulphate from lead carbonate.)
    Ans. Treatment with dil. nitric acid to form soluble lead nitrate.
  2. Write the equation for the reaction that will take place when this first step is carried out.
    Ans. PbCO3 + 2HNO3 → Pb(NO3)2 + H20 + CO2↑
    Insoluble
  3. Why is the direct addition of dil. H2SO4 to PbCO3 an impractical method of preparing lead sulphate.
    Ans. Direct addition of dil. sulphuric acid to lead carbonate will lead to deposition of lead sulphate on the surface of lead carbonate which stops further reaction of sulphuric acid on it.

Question 4.

Fill in the blanks:
An acid is a compound which when dissolved in water forms hydronium ions as the only
(1) ….  ions. A base is a compound which if soluble in water contains (2)…. ions. A base reacts with an acid to form a (3)…… and water only. This type of reaction is known as (4)…….
Answer:

  1. Positive
  2. Hydroxyl
  3. Salt
  4. neutralization.

Question 5.

Acid dissolve in water to produce positively charged ions. Draw the structure of these ions
Answer:
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 2

Question 6.

Name the ion other than ammonium ion formed when ammonia dissolves in water. Give one test that can be used to detect the presence of the ion product.
Answer:
Hydroxide ion.

2006

Question 1.

Mention the colour changes observed when the following indicators are added to acids:

  1. Alkaline phenolphthalein solution.
    Ans. Pink solution becomes colourless
  2. Methyl orange solution
    Ans. Orange solution changes to red or pink
  3. Neutral litmus solution
    Ans. It turns red

Question 2.

Which of the following hydroxides is not an alkali – (Choose from the choices A, B, C and D)
(A) ammonium hydroxide
(B) calcium hydroxide
(C) copper hydroxide  
(D) sodium hydroxide

2007

Question 1.

Complete the blanks from the list given:

Ammonia, Ammonium, Carbonate, Carbon dioxide, Hydrogen, Hydronium, Hydroxide, Precipitate, Salt, Water. A solution X turns blue litmus red, so it must contain (1) …. ions ; another solution Y turns red litmus blue and therefore, must contain (2)……. ions. When solutions X and Y are mixed together the products will be a (3) …. and (4) If a piece of magnesium were put into solution X, (5)….. gas would be evolved.
Answer:

  1. hydronium
  2. hydroxide
  3. salt
  4. water
  5. hydrogen

Question 2.

Match the following:
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 3

New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 4
Answer:
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 5

Question 3.

Write balanced equation for formation of PbCl2 from Pb(NO3)2 soln. and NaCl soln.
Answer:
Pb(NO3)2 + 2NaCl → PbCl2 + 2NaNO3

2008 

Question 1.

What is the term defined i) A base which is soluble in water.
Answer:
Alkali.

2009

Question 1.

The acid which contains four hydrogen atoms –
(1) Formic acid
(2) Sulphuric acid
(3) Nitric acid
(4) Acetic acid

Question 2.

A black coloured solid which on reaction with dilute sulphuric acid forms a blue coloured solution is:
(A) Carbon
(B) Managanese (IV) oxide
(C) Lead (II) oxide
(D) Copper (II) oxide

Question 3.

Solution A is a strong acid
Solution B is a weak acid
Solution C is a strong alkali

Question 3(1).

Which solution contains solute molecules in addition to water molecules ?
Answer:
Solution B — weak acid

Question 3(2).

Which solution will give a gelatinous white precipitate with zinc sulphate solution? The precipitate disappears when an excess of the solution is added.
Answer:
Solution C — strong alkali

Question 3(3).

Which solution could be a solution of glacial acetic acid ?
Answer:
Solution B — weak acid

Question 3(4).

Give an example of a solution which is a weak alkali.
Answer:
Ammonium hydroxide — weak alkali

Question 4.

Write the equation(s) for the reaction(s) to prepare lead sulphate from lead carbonate.
Answer:
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 6

Question 5.

Define the following terms : Neutralization
Answer:
Neutralisation: The reaction in which an acid reacts with a base to form salt and water is known as neutralisation.
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 7

2010

Question 1.

A: Nitroso Iron (II) sulphate
B: Iron (III) chloride
C: Chromium sulphate
D: Lead (II) chloride
E: Sodium chloride.
Select from A, B, C, D and E –

  1. A compound soluble in hot water but insoluble in cold water.
  2. A compound which in the aqueous solution state,is neutral in nature.
  3. A deliquescent compound.

Answer:

  1. Lead (II) chloride
  2. Sodium chloride
  3. Iron (II) chloride

Question 2.

Select the correct answer from A, B, C and D –

(1) A weak organic acid is:
A: Formic acid  
B: Sulphuric acid
C: Nitric acid
D: Hydrochloric acid

(2) A complex salt is:
A : Zinc sulphate
B : Sodium hydrogen sulphate
C : Iron (II) ammonium sulphate
D : Tetrammine copper (II) sulphate

Question 3.

Give an equation for the conversions

  1. ZnSO4 to ZnCO3
  2. ZnCO3 to Zn(NO3)2

Answer:
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 8

Question 4.

A: NaOH sol. : B: weak acid C: Dil. H2SO4
Select the one which contains solute ions and molecules.
Answer:

  1. Solution C
  2. Solution A
  3. Solution B

Question 5.

Give balanced equation/s for the preparation of the following salts:

  1. Copper (II) sulphate from CuO.
  2. Iron (III) chloride from Fe.
  3. K2SO4 from KOH sol.
  4. Lead (II) chloride from PbCO3 (give two equations)

Answer:
(1)
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 9

(2)
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 10

(3)
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 11

(4)
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 12

2011

Question 1.

Write the balanced chemical equation: Lead nitrate solution is added to sodium chloride solution
Answer:
Pb (NO3)2 + 2NaCl → PbCl2 + 2NaNO3

Question 2.

Name the method used from the list:
A: Simple displacement
B: Neutralization
C: Decomposition by acid
D: Double decomposition
E: Direct synthesis

For preparation of the following salts –

  1. Sodium nitrate
  2. Iron (III) chloride
  3. Lead chloride
  4. Zinc sulphate
  5. Sodium hydrogen sulphate.

Answer:
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 13

2012

Question 1.

Match the following:
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 14
Answer:
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 15

2013

Question 1.

Select the words given below which are required to correctly complete the blanks –
[ammonia, ammonium, carbonate, carbon dioxide, hydrogen, hydronium, hydroxide, precipitate, salt water]:

  1. A solultion M turns blue litmus red, so it must contain
    (1)………..ions ; another solution O turns red litmus blue and hence, must contain, (2)……… ions.
  2. When solution M and O are mixed together, the prod­ucts will be (3)………. and (4) ……………..
  3. If a piece of magnesium was put into a solution M,(5)……………..gas would be evolved.

Answer:
(1) hydronium (2) hydroxide (3) salt (4) water (5) hydrogen.

Question 2.

Give a suitable chemical term for:

  1. A salt formed by incomplete neutralisation of an acid by a base.
  2. A definite number of water molecules bound to some salts.

Answer:

  1. Acid salt
  2. Water of crystallisation

Question 3.

Choosing the substances from the list given:
dil. Sulphuric acid, Copper, Iron, Sodium, Copper (II) carbonate, Sodium carbonate, Sodium chloride, Zinc nitrate
Write balanced equations for the reactions which would be used in the laboratory to obtain the following salts:

  1. Sodium sulphate
  2. Zinc carbonate
  3. Copper (II) sulphate
  4. Iron (II) sulphate.

Answer:

  1. Sodium sulphate
    Na2CO3 + H2SO4 → Na2SO4 + HzO + CO2

  2. Zinc carbonate
    Zn(NO3)2 + Na2CO3→ ZnCO3 + 2NaNO3
  3. Copper (II) sulphate
    CuCO3 + H2SO4 → CuSO4 + h2o + CO2
  4. Iron (II) sulphate.
    Fe + H2SO4 → FeSO4 + H2

Question 4.

Identify: An acid which is present in vinegar.
Answer:
Acetic acid or ethanoic acid.

2014

Fill in the blank from the choices given:

Question 1.

The basicity of Acetic Acid is 1.

Question 2.

Draw the structure of the stable positive ion formed when an acid dissolves in water.
Answer:
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 16

Question 3.

State the inference drawn from the following observations:
Salt S is prepared by reacting dilute sulphuric acid with copper oxide. Identify S.
Answer:
The compound or salt S is copper sulphate CuSO4
CuO + H2 SO4  → CuSO4 + FlO

Question 4.

Give balanced chemical equations to prepareation of the following salts:

  1. Lead sulphate-from lead carbonate.
  2. Sodium sulphate-using dilute sulphuric acid.
  3. Copper chloride-using copper carbonate.

Answer:

(1) Lead sulphate from lead carbonate.

PbCO3 + HNO3 → Pb(NO3)2 + H2O  + CO2
Pb(NO3)2 + H2SO4  → PbSO4 + 2HNO3

(2) Sodium sulphate using dilute sulphuric acid.

Na2CO3  + H2SO4(dil) → Na2SO4  +  H2O+ CO2

(3) Copper chloride using copper carbonate.

CuCO3  +   HCl(dil) → CuCl2   +   H2O  + CO2
(Insoluble)

2015

Question 1.

Give balanced chemical equations for the following conversions.Fe→ Fed,
Fe →FeCl3
Answer:
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 17
Question 2.

From the list of salts — AgCl, MgCl2, NaHSO4, PbCO3, ZnCO3, KNO3, Ca(NO3)2 Choose the salt that most appropriately fits the descrip­tion given below:

  1. A deliquescent salt.
  2. An insoluble chloride.

Answer:

  1. A deliquescent salt = MgCl2
  2. An insoluble chloride=AgCl

Question 3.

From the following list of oxides — SO2, SiO2, Al2O3, MgO, CO, Na2O -Select an oxide which dissolves in water forming an acid.
Answer:
SO2

2016

Fill in the blank:

Question 1.

Higher the pH value of a solution, the more………… (acidic / alkaline) it is.
Answer:
Higher the pH value of a solution, the more alkaline it is.

Question 2.

Match the following salts given below:

(1) Pb(NO3)2 from PbO
(2) MgCl2 from Mg
(3) FeCl3 from Fe
(4) NaNO3 from NaOH
(5) ZnCO3 from ZnSO4
With their correct method of preparation from: A, B, C, D and E.
(A) Simple displacement
(B) Titration
(C) Neutralization
(D) Precipitation
(E) Combination
Answer:
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 18

2017

1. Fill in the blanks from the choices given in brackets –

Question 1.

When a metallic oxide is dissolved in water, the solution formed has a high concentration of________ ions. [H+,H3O+, OH ]
Answer:
When a metallic oxide is dissolved in water, the solution formed has a high concentration of OH” ions.

Question 2.

.Choose the correct answer from the options –
(1) to increase the pH value of a neutral solution, we should add: A. An acid; B. An acid salt; C. An alkali; D. A salt,
(2) Anhydrous iron [in] chloride is prepared by:
(A) direct combination;
(B) Simple displacement;
(C) Decomposition;
(D) Neutralization.
Answer:
C. an alkali

Question 3.

Write a balanced chemical equation for the preparation of each of the following salts:

  1. Copper carbonate,
  2. Ammonium sulphate crystals.

Answer:
CuSO4(aq) + Na2CO3(uq) → Na2SO4(aq) + CuCO3(s)
2NH4OH(aq) + H2SO4(aq) → (NH4)2SO4 + 2H2O

Additional Questions

Question 1.

Define the following as per ionic theory with examples and ionic equations wherever relevant
(1) acid
(2) base
(3) alkali
(4) neutralization
Answer:
(1) Acid — An acid is a compound which when dissolved in water yields – hydronium ions (H3O+ ) as the only positively charged ion.
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 19

(2) Base — A base is a compound which reacts with hydronium ions of an acid – to give salt and water

CuO + 2HCl → CuCl2 + H2O

(3) Alkali — An alkali is a compound which when dissolved in water yields Hydroxyl ions (OH–) as they are negatively charged ions.
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 20
Alkali is a base soluble in water.

(4) Neutralization — | H+| ions of an acid completely or combine with |OH+| ions of a base to give salt and water only.

Acid + Base → Salt + Water
HCl + NaOH → NaCl + H2O

Question 2.

Differentiate between:

  1. Organic and inorganic acids
  2. Hydracids and oxyacids with examples.

Answer:
(1)
Organic acids – Those acids which are derived from plants, e.g., citric acid, acetic acid, tartaric acid Inorganic acids – Acids derived from minerals e.g. HCl2,h2SO4
(2)
Hydracids – Acids containing hydrogen and a non-metallic element other than oxygen, e.g. HCl, HBr, HI.
Oxyacids – Acids containing hydrogen, another element and oxygen, e.g. HNO3, H,SO4.

Question 3.

State on what basis does the strength of an acid and an alkali depend on.
Answer:
Strength of acids depends upon concentration of hydronium ion |H3O+| present in an aqueous solution
of an acid. Strength of alkali depends on the concentration of the hydroxyl ions |OH–| present in an aqueous solution of an alkali.

Question 4.

Differentiate between (1) strong and weak acid (2) strong and weak alkali with suitable examples and ionic equations.
Answer:
(1) Strong Acid – Is an acid which dissociates – almost completely in aqueous solution there by producing a – high concentration of hydrogen [H+] ions [or H3O+ions]
Examples: Hydrochloric, Sulphuric and Nitric acid.

New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 21
Weak Acid – Is an acid which dissociates – only partially in a aqueous solution thereby producing a – low concentration of hydrogen [H+] ions [or H3O+ ions].
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 22

(2) Strong Alkali – Is an alkali which dissociates – almost completely in aqueous solution thereby producing a – high concentration of hydroxyl [OH–] ions.
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 23

Examples: Lithium, Sodium and Potassium hydroxide
Weak alkali – Is an alkali which dissociates – only partially in aqueous solution thereby producing a – low concentration of hydroxyl [OH– ] ions.
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 24
Examples: Ammonium hydroxide and Calcium hydroxide.

Question 5.

Name the ions formed when – HCl ; HNO3 ; H2SO4 ; CH3COOH ; NaOH and NH4OH ionise in aq. soln.
Answer:
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 25

Question 6.

State giving reasons which is a stronger acid – dil. HCl or cone. H2CO3.
Answer:
Dil. HCl is a stronger acid than cone. H2CO3
Reason: HCl ionises almost completely in aqueous solution thereby producing a high concentration of Hp ions in aqueous solution. On the other hand, H2CO3 ionises to a very small extent producing a low
concentration of HO+ ions. More the concentration of H3O+ ions in solution, stronger is the acid. Hence dil. HCl is a stronger acid than cone. H2CO3.

Question 7.

State why the basicity of acetic acid is one and acidity of calcium hydroxide is two.
Answer:
Basicity of an acid is the number of hydrogen ions which can be produced from one molecule of the acids on complete dissociation. Acetic acid, CH.COOH gives one H+ per molecule the acid, hence acetic acid is monobasic i.e., its basicity is one.
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 26
Acidity of a base is the number of hydroxyl ions which can be produced from one molecule of the base on complete dissocation. Ca(OH)2 (calcium hydroxide) gives two hydroxyl ions per molecule of the base, hence calcium hydroxide is diacidic i.e., its acidity is two.

Question 8.

Give three reasons with equations wherever required, why sulphuric acid is a dibasic acid.
Answer:
Sulphuric acid (H2SO4) is a dibasic acid as explained below:

(1)
It ionises in aqueous solution to produce two hydrogen ions per molecule of the acid.

OR

It contains two replace all hydrogen ions per molecule of the acid.
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 27

(2)
It ionises in two steps in aqueous solution as shown below:
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 28

(3)
It forms two types of salt, e., normal salt and acid salt as shown below:
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 29

Question 9.

State how acids are defined as per Arrhenius’s and Lowry – Bronsted’s theory.
Answer:
Arrhenius Theory –
Acids are substances which – dissociate in aqueous solution to give H+ ions.
Strong acids dissociate – almost completely, while weak acids dissociate partially.

Question 10.

Oxygen atom in water has two Hone pair of electrons’. Explain the meaning of the term in italics. With the help of an electron dot diagram show the formation of hydronium ion and ammonium ion from a water molecule and an ammonia molecule respectively.
Answer:
A pair of electrons not shared with any other atom for bond formation is called a lone pair of electrons. In water, the central atom – oxygen has two lone pair of electrons as shown ahead:

Structure of water molecule
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 30

Formation of hydronium ion- (H3O+): When an acid is dissolved in water the proton (H+) released by the acid add onto the lone pair electrons of the oxygen atom of a water molecule. The proton (H+) accepts the lone pair of electrons forming a coordinate bond (shown by an arrow).
HCl  → H+ + Cl–
Water Proton Hydronium ion
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 31

Formation of ammonium ion (NH4+): When ammonia gas is dissolved in water, the proton released by water adds onto the lone pair of electrons of the nitrogen atom of the ammonia molecule. The proton (H+) accepts the lone pair of electrons forming a coordinate bond (shown by an arrow).
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 32
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 33

Question 11.

State how you would obtain:

  1. Sulphuric acid from an acidic oxide
  2. KOH from a basic oxide.

Answer:
(1)
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 34
(2)
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 35

Question 12.

State two chemical properties each with equations of a solution containing
(1) H+ ions
(2) OH
Answer:
(1) Properties of a solution containing H+ ions: Acids when dissolved in water produce H2O+ or H ions. Typical chemical properties of aqueous solution of acids are:

(a) Neutralisation: H+ ions react with OH ions from alkalies to give water
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 36
(b) Reaction with active metals: Active metals like Al, Zn, Fe, etc., react with dil. acids (HCl, H2SO4) to give hydrogen gas. In this reaction H+ is reduced to H, by the active metal. For example,
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 37

(2) Properties of solution containing OH– ions: Alkalies when dissolved in water produce OH” ions. Typical reaction of aqueous solution of alkalies are;

(a) Neutralisation: OH+ ions react with H+ ions from acids to give water.
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 38

(b) Reaction with solutions of metallic salts: Hydroxides of metals other than Group 1 and 2 are generally insoluble in water. Such hydroxides are precipitated from their respective salt solutions by OH” ions. For example,
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 39

Question 13.

Give equations for the decomposition of a metallic
(1) chloride
(2) nitrate with cone. H2SO4.
Answer:
(1) Reaction of cone. H2SO4 with metallic chloride:
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 40
(2) Reaction of cone. H2SO4 with metallic nitrate
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 41

Question 14.

State in the above reactions a reason for the formation of the respective acids from cone. H2SO4.
Answer:
The reason for the formation of the respective acids from cone. H2SO4 is the volatility of the acid formed. At room temperature or above HCl is a gas while HNO3, which is a liquid at room temperature, volatileses at the reaction temperature (w 200°C).

Question 15.

Convert
(1) NaHCO3
(2) Na2CO3 to unstable carbonic acid by action with dil. H2SO4.
State the reason why ammonia is evolved when an ammonium salt and alkali are heated.
Answer:

  1. 2NaHCO3 + H2SO4 (dil.) → Na2SO4 + 2H2CO3
  2. Na2CO3 + H2SO4 (dil.) → Na2SO4 + H2CO3

Ammonia is evolved when an ammonium salt and alkali are heated.
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 42
This is because a non-volatile base, Ca(OH)2 displace a volatile base, NH4OH which decomposes to given NH3 and H2O.

Question 16.

Define pH value. What would you say about the pH of a solution in which (i) H+ ions = OH– ions

  1. evolves CO2when heated with Na2CO3
  2. OH” ions > H+ ions.

Answer:
pH value: The pH value of a solution is defined as the negative logarithm (to the bsise 10) of the hydrogen ion concentration expressed in mol L-1. Thus,
PH = -log10 [H+]
Where [H+] stands for hydrogen ion concentration in mol L-1.

  1. A solution in which [H+] = [OH–], is neutral with pH = 7.
  2. A solution which evolves CO2 with NaCO3 is acidic in nature with pH < 7.
  3. A solution in which [OH–] > [H+] is basic in nature with pH >7.

Question 17.

State whether litmus is a common acid-base indictor or a universal indicator.
Answer:
Litmus is a common acid-base indicator. It is not a universal indicator.

Question 18.

State the colour change in a neutral litmus in presence of
(1) acidic
(2) alkaline medium.
Answer:
Neutral litmus is purple in colour

  1. In acidic medium colour of neutral litmus changes from purple to red.
  2. In alkaline medium colour of neutral litmus changes from purple to blue.

Question 19.

State the colour change in a universal indicator e.g. pH paper on

  1. slightly acidic soil
  2. slightly alkaline soil
  3. dairy milk
  4. human blood tested for medical diagnosis.

Answer:

  1. In slightly acidic soil colour of universal indicator changes to yellow.
  2. In slightly alkaline soil colour of universal indicator changes to blue.
  3. In dairy milk colour of universal indicator change to green.
  4. In human blood colour of universal indicator changes to green (pH = 7.3).

Question 20.

Define
(1) salt
(2) normal salt
(3) acid salt – with relevant examples and equations.
Answer:
(1) Salts: A salt is a compound formed by partial or complete replacement of the replaceable hydrogen ions of an acid by a metallic ion or ammonium ion.
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 43

(2) Normal salt: The salt formed by complete replacement of the replaceable hydrogen ions present in a molecule of the acid by metallic or ammonium ion. For example,
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 44
2NaOH(aq) + H2CO3(aq)→ Na2CO3(aq) + 2H2O (l)

NH4OH(aq) + HCl(aq)→ NH4Cl(aq) + H.O (l)

(3) Acid salt: The salt formed by partial replacement of the replaceable hydrogen ions present in a molecule of the acid by metallic or ammonium ion. For example,

NaOH(aq) + H3PO4(aq) → NaH2PO4(aq) + H2O(l)
2NaOH(aq) + H3PO4(aq)→Na2HPO4(aq) + 2H2O (l)
KOH(aq) + H2SO4(aq)→ KHS04(aq) + H2O(l)
NH4OH(aq) + H2CO3(aq)→NH4HCO3(aq) + H.O (l)

Question 21.

State:

  1. the formation
  2. the components of – a basic salt.

State which of following salts is an – acid, normal or basic salt.

  1. bleaching powder
  2. potassium mercuric iodide
  3. sodium sulphite
  4. sodium hydrogen sulphite
  5. sodium silver cyanide
  6. basic lead nitrate
  7. potassium zincate
  8. alum
  9. calcium bicarbonate
  10. basic copper chloride
  11. trisodium phosphate.

Answer:

(1) Formation of a basic salt: A basic salt is formed by partial replacement of hydroxyl group of a diacidic or triacidic base with an acid radical (or an anion other than OH).

(2) Components of a basic salt: A basic salt contains a cation (other than H+ ion), a hydroxyl ion (OH– from base) and an anion (other than OH– ion). For example,
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 45

  1. Bleaching powder, CaOCl, (Normal salt/Mixed salt)
  2. Potassium mercuric iodide, K2(HgI4) .
    (Normal salt/Complex salt)
  3. Sodium sulphate, Na2SO4 (Normal salt)
  4. Sodium hydrogen sulphite, NaHSO3 (Acid salt)
  5. Sodium silver cyanide, Na[Ag(CN)2]
    (Normal salt/Complex salt)
  6. Basic lead nitrate, Pb(OH)NO3 (Basic salt)
  7. Potassium zincate, K2ZnO2 (Normal salt)
  8. Alum or potash alum, K2SO4.Al2(SO4)3.24H2O
    (Normal salt/Double salt)
  9. Calcium bicarbonate, Ca(HCO3)2 (Acid salt)
  10. Basic copper chloride, Cu(OH)Cl (Basic salt)
  11. Trisodium phosphate, Na3PO4 (Normal salt)

Question 22.

Name three (1) sulphates (2) chlorides insoluble in water and – two (1) oxides (2) carbonates soluble in water.
Answer:
(1) Three sulphates insoluble in water
Lead sulphate (PbSO4), Calcium sulphate (CaSO4), and Barium sulphate (BaSO4).

(2) Three chloride insoluble in water
Silver chloride (AgCl), Lead chloride (PbCl2), and Mercury chloride (Hg2Cl2 or HgCl).

(1) Two oxides soluble in water
Sodium oxide (Na2O  ), and Potassium oxide (K2O)

(2) Two carbonates soluble in water
Sodium carbonate (Na2CO3), and Ammonium carbonate [(Na4)2CO3]

Question 23.

State the method only, generally used for the preparation of the following salts
(1) Zn(NO3)2
(2) NH4Cl
(3) ZnSO4
(4) ZnS
(5) CaCO3
(6) FeCl3
(7) PbCl2
(8) Pb(NO3)2–
Answer:

Salt

Method of preparation

1.      Zn(NO3)2Neutralisation of insoluble base by acid/Decomposition of insoluble carbonate by acid
2.      NH4ClNeutralisation (titration) of soluble  base by acid/Decomposition of soluble carbonate by acid
3.      ZnSO4Neutralisation of insoluble base by acid/Decomposition of insoluble carbonate by acid
4.      ZnSDirect combination (Synthesis)/Double decomposition (Precipitation)
5.      CaCO3Double decomposition (Precipitation)
6.      Fecl3Direct combination (Synthesis)/
7.      pbCl2Double decomposition (Precipitation)
8.      Pb(NO3)2Neutralisation of insoluble base by acid/Decompostion of insoluble carbonate by acids

Question 24.

Give balanced equations for the preparation of the following salts –

(a)
(1) CuSO4  
(2) NaHSO4
(3) Na2SO4
(4) FeSO4
(5) BaSO4
(6) PbSO4 – using dil. H2SO4
(b)
(1) NaHSO4
(2) CuSO4 – using cone. H2SO4.
Answer:
(a) Using dil. H2SO4

  1. CuO (s) + H2SO4 (aq) → CuSO4 (aq) + 2H2O (l)
  2. NaOH (aq) + H2SO4 (aq) → NaHSO4 (aq) + H2O(l)
  3. 2NaOH (aq) + H2SO4 (aq)→Na2SO4 (aq) + 2H2O(l)
  4. Fe (s) + H2SO4 (aq)→ FeSO4 (aq) + H2 (g)
  5. BaCl2 (aq) + H2SO4 (aq)→ BaSO4 (s) + 2HCl (aq)
  6. Pb(NO3)2 + H2SO4 (aq)→ PbSO4 (s) + 2HNO3 (aq)

(b) Using cone. H2SO4

New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 46

Question 25.

Starting from insoluble ZnO how would you obtain insoluble ZnCO3 by precipitation.
Answer:
ZnO (s) + 2HCl (aq)→ ZnCl2 (aq) + H2O(l)
ZnCl2 (aq) + Na2CO3 (aq)→ ZnCO3 (s) + 2NaCl (aq)

Dissolve zinc oxide in minimum quantity of dil. HCl. Add to it a saturated solution ofNa2CO3 in water till
no more precipitation takes place. Filter and dry the ZnCO3 so obtained.

Question 26.

Give balanced equations for the action of a dilute acid on
(1) zinc carbonate,
(2) potassium bicarbonate for the preparation of the respective salt.
Answer:

  1. Zinc carbonate
    ZnCO3 + 2HNO3 → Zn(NO3)2 + H2O + CO

  2. Potassium bicarbonate
    2KHCO3 + H2SO4 → K2S04 + 2H2O + 2CO2

Question 27.

Give balanced equations for the decomposition of
(1) calcium bicarbonate by dil. HCl,
(2) calcium carbonate by dil. HNO3,
(3) sodium sulphite by dil. H2SO4,
(4) zinc sulphide by dil. H2SO4.

Answer:

  1. Ca(HCO3)2 + 2HCl→ CaCl2 + 2H2O+ 2CO2
  2. CaCO3 + 2HNO3 → Ca(NO.)2 + H2O+ CO2
  3. Na2SO3 + H2SO4 (dil.) → Na2SO4 + H2O+ SO2
  4. ZnS + H2SO4 →ZnSO4 + H2S

Question 28.

State what will be the effect of each of the following solution on blue litmus –
(1) K2CO3 soln
(2) KCl soln.
(3) NH4NO3
Answer:

  1. K2CO3 is a salt of a strong base (KOH) and weak acid (H2CO3). Hence its aqueous solution will be basic in nature. It will have no effect on blue litmus solution.
  2. KCl is a salt of a strong acid (HCl) and a strong base (KOH). Hence its aqueous solution will be neutral in nature. It will have no effect on blue litmus solution.
  3. NH4NO3 is a salt of a strong acid (HNO3) and weak base (NH4OH). Hence its aqueous solution will be acidic in nature. It will turn blue litmus solution red.

Question 29.

Select the correct acid, base or salt from the list in bracket for each of the statements given below:

  1. An example of an acid derived from a mineral is……….. (citric acid / nitric acid / acetic acid)
    Ans. Nitric acid
  1. An example of a base which is not a alkali is….. (caustic soda / zinc hydroxide / liquor ammonia / caustic potash)
    Ans. Zinc hydroxide
  1. An example of a strong acid is dilute……… (acetic acid / sulphuric acid / tartaric acid / carbonic acid)
    Ans. Sulphuric acid
  1. An example of a weak alkali is…. (potassium hydroxide / calcium hydroxide / sodium hydroxide) solution.
    Ans. Calcium Hydroxide
  1. An acid having basicity 1 is……… (carbonic acid / acetic acid / sulphurous acid)
    Ans. Acetic acid
  1. An acid obtained by dissolving sulphur trioxide in water is…. (sulphurous acid / sulphuric acid oleum)
    Ans. Sulphuric acid
  1. A volatile acid obtained when nitre reacts with non­volatile concentrated sulphuric acid on heating is (hydrochloric acid / sulphuric acid/ nitric acid)
    Ans. Nitric acid
  1. A base obtained when lead nitrate undergoes thermal decomposition is……. (trilead tetroxide / lead (IV) oxide/ lead (II) oxide.                                                        .
    Ans. Lead (II) oxide
  1. An acid obtained when concentrated nitric acid is heated with sulphur is…….. (sulphurous acid / sulphuric acid / nitrous acid)
    Ans. Sulphuric acid
  1. The more volatile acid obtained when the less volatile acid reacts with sodium bicarbonate is……… (sulphuric acid / carbonic acid / nitric acid)
    Ans. Carbonic acid
  1. The insoluble base obtained when sodium hydroxide reacts with iron (III) chloride is…. (iron (II) hydroxide / iron (III) hydroxide / iron (II) oxide)
    Ans. Iron (III) hydroxide.
  1. A solution whose pH is above 7 is….. (vinegar / milk / liquor ammonia.
    Ans. Liquor Ammonia
  1. The salt formed when sulphuric acid reacts with excess caustic soda solution is…… (sodium bisulphite / sodium sulphate / sodium sulphite / sodium bisulphate).
    Ans. Sodium sulphate
  1. An example of an acid salt is……. [CH3COONa/NaNO3/ Na2HPO4/NaKCO3]
    Ans. Na2HPO4
  1. An example of a soluble salt is ……… (AgCl / PbSO4 /CaSO4 / CaCl2)
    Ans. CaCl2
  1. An example of an insoluble salt is….. (Na2CO3 \ K2CCl,/ MgCO3 / (NH4)2 CO3)
    Ans. MgCO3
  1. A salt prepared by neutralization in which titration is involved is…….. (MgCl2 / CaCl2 / NH,Cl / CuCl2)
    Ans. NH4Cl
  2. An insoluble salt prepared by direct combination or synthesis is……. [FeCl3 / FeSO4 / FeS/Fe(NO3)2] Ans. FeS
  1. A salt prepared by precipitation i.e. by double decomposition of two salt solutions is………… (Na2SO4 /PbSO4 / ZnSO4 / CuSO4)
    Ans. PbSO.
  2. A salt prepared by simple displacement i.e. action of dilute acid on a metal is____ (PbCl2/ CuCL, / AlCl3 / HgCl)
    Ans. AlCl3
  3. Decomposition of calcium hydrogen carbonate with…. [dil. HNO3 /dil. HCl/dil. H2SO4] results in formation of calcium chloride.
    Ans. dil.HCl
  1. Action of dilute acid on a metallic sulphide results in evolution of____ [SO2/H2S/CO2] gas.
    Ans. H2S
  1. A salt which on hydrolysis produces a neutral solution is……. (sodium chloride / ammonium chloride / sodium carbonate)
    Ans. Sodium chloride

Unit test Paper 3 A —Acids, Bases and Salts

l. Name the following:

  1. A basic solution which does not contain a metallic element.
    Ans. Ammonium Hydroxide.
  1. A normal salt of sodium formed from acetic acid.
    Ans. Sodium acetate, COCOON a.
  2. A base which reacts with an acid to give a salt which .on hydrolysis gives a slightly acidic solution.
    Ans. Ammonium hydroxide (NH4OH)

OR

   Calcium hydroxide [Ca(OH)2].

  1. An ion which combines with a polar covalent molecule to form an ammonium ion.
    Ans. Hydrogen ion a proton (H+).
  1. A soluble salt formed by direct combination between a light metal & a greenish yellow gas.
    Ans. AlCl3

2. Identify which of the following terms matches with the appropriate description 1 to 5.
A: Hydracid
B: Monobasic acid
C: Less volatile acid
D: Weak acid
E: Tribasic acid
F: Dibasic acid
G: More volatile acid

  1. An acid having basicity 1 and having only one replaceable hydrogen ion per molecule of the acid.
    Ans. Monobasic acid
  1. An acid which dissociates to give a low concentration of H+
    Ans. Weak acid
  1. An acid containing hydrogen and a non-metallic element other than oxygen.
    Ans. Hydracids.
  1. The type of acid which generally displaces another acid when the acid is heated with a salt.
    Ans. Less volatile acid
  1. The type of acid which reacts with a base to give an acid salt and a normal salt.
    Ans. Dibasic acid

3. State which of the following methods is generally used for preparing the salts 1 to 5 given below:

A: Neutralisation – insoluble base and dil. acid
B: Neutralisation – alkali and dil. acid
C: Simple displacement – active metal and dil. acid
D: Direct combination
E: Precipitation (double decomposition)                 .

  1. PbCO3
  2. Zn(NO3)2
  3. NaCl
  4. Cu(NO3)2
  5. FeS

Answer:

  1. PbCIO3: Precipitation (Double decomposition) (E)
  2. Zn(NO3)2: Simple displacement-active metal and dil. acid (C)
  3. NaCl: Neutralisation-alkali and dil. acid (B)
  4. (CuNO3)2: Neutralisation + insoluble base and dil. acid (A)
  5. FeS: Direct combination (D)

4. Give balanced equations for the preparation of the following salts:

  1. Calcium oxide → Calcium chloride → Calcium carbonate
    Ans. CaO + 2HCl → CaCl2 + H2O
  2. Zinc sulphide Zn→ Zinc sulphate
    Ans. Zn + S → ZnS
  3. Iron (II) chloride ← Fe→ Iron (III) chloride
    Ans. Fe + 2HCl → FeCl2 + H2
  4. Lead (II) oxide → Lead nitrate→ Lead sulphate
    Ans. PbO + 2HNO3 → Pb(NO3)2 + H2O
  5. Copper (II) oxide → Copper (II) sulphate ←Copper (II)hydroxide
    Ans. CuO + H2SC4 → CuSO4+ H2O

5. The diagram represents the preparation of sodium sulphate salt from dil. H2SO4 acid and sodium hydroxide.
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 47

  1. Name the apparatus ‘A’.
    Ans. Burette
  1. Name the substance ‘X’ placed in ‘A’ and the (substance ‘Y’ placed in B.
    Ans. Dil. H2SO4 Sodium Hydroxide
  1. State the reason for conducting the titration using the apparatus ‘A’ and ‘B’
    Ans. Titration is conducted to determine the completion of the neutralisation reaction, i.e. to determine the amount of sulphuric acid required to neutralise a known amount of sodium hydroxide.
  1. State which solution is transferred to the evaporating dish and evaporated to point of crystallisation for obtaining the salt.
    Ans. Sodium Sulphate.
  1. State why titration is not conducted for the preparation of copper (II) sulphate crystals by neutralisation.
    Ans. This is because copper (II) oxide is not soluble in water.

6. Give reasons for the following:

Question 6(1).

Concentrated sulphuric acid is a weaker acid compared to dilute sulphuric acid.
Answer:
Sulphuric acid,H2SO4 is a covalent compound as shown below.
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 48
When dissolved in water, polar water molecules helps in its ionisation, thus producing B,O+ ions responsible for its acidic nature. More water (i.e., dilute acid) means more H3O+ ions and hence stronger acid.

Question 6(2).

An aqueous solution of the salt ammonium chloride is acidic in nature while an aqueous solution of sodium chloride is neutral.
Answer:

New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 49
New Simplified Chemistry Class 10 ICSE Solutions Chapter 3A Acids, Bases and Salts 50

From above equation it is clear that NH4Cl forms weak alkali which is acidic in nature where as NaCl from strong alkali which is neutral.

Question 6(3).

In the preparation of an insoluble salt from another insoluble salt by precipitation [double decomposition], dilute nitric acid and not dilute sulphuric acid is generally used.
Answer:
Direct addition of dil. H2SO4 to PbCO3 is an impractical method of preparing lead sulphate since PbSO4 is insoluble and forms a coating on PbCO3, thereby the reaction slowly comes to a stop.

Question 6(4).

Acetic acid does not form an acid salt but forms a normal salt.
Answer:
Acetic acid (CH3COOH) is a monobasic acid, i.e. it contains only one replaceable hydrogen ion per molecule of the acid. As such it can only form normal salts.

Question 6(5).

Sulphurous acid forms two types of salts on reaction with an alkali.
Answer:
Sulphurous acid (H2SO3) is a dibasic acid, i.e., it contains two replaceable hydrogen ions per molecule. As such, it can form normal salt (say Na2SO3) as well as acid salt (NaHSO3) on reaction with an alkali.

 

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