Frank ICSE Solutions for Class 9 Chemistry

Frank ICSE Solutions for Class 9 Chemistry – The Language of Chemistry

by

Frank ICSE Solutions for Class 9 Chemistry – The Language of Chemistry

PAGE NO :56
Solution 1:
Symbol – It is the short form or abbreviation used for the name of an element. It represents one atom of that element.
Formula – Formula of a compound represents the composition of a molecule of the substance in terms of the symbols of the elements present in the molecule.

Solution 2:

  1. CaCO3
  2. MgSO4
  3. Fe2 (SO4)3
  4. CaHCO3
  5. CuI
  6. K2Cr2O7
  7. KMnO4
  8. Na2SO4
  9. Mg (NO3)2
  10. Ca3 (PO4)2

Solution 3:

  1. Valency – The combining capacity of an element is called its valency.
  2. Helium < Sodium < Magnesium < Carbon < Phosphorous

Solution 4:
Law of conservation of matter governs a completely balanced equation. It states that “matter can neither be created nor destroyed.”

Solution 5:
A symbol signifies one atom of that element.

Solution 6:
Latin names of the following compounds are-
Iron                      –   Ferrum
Tin                        –   Stannum
Lead                     –   Plumbum
Sodium                –   Natrium
Potassium           –   Kalium
Mercury              –   Hydragyrum

Solution 7:
The equation in which the total number of atoms of each element in the reactants, on the left side of the equation is same as the number of atoms in the products formed, on the right side of the equation is called as balanced chemical equation.

Solution 8:
Frank ICSE Solutions for Class 9 Chemistry - The Language of Chemistry 1

Solution 9:
A chemical equation gives information about-

  1. What substances enter into a given reaction (reactants) and what products are formed as a result of the reaction.
  2. The  quantities of the reactants and the product formed.
  3. The  optimum conditions of temperature and pressure.

Solution 10:
Frank ICSE Solutions for Class 9 Chemistry - The Language of Chemistry 2

Solution 11:
H2 means hydrogen, O4 means oxygen and S means sulphur  in the formula of H2SO4.

Solution 12:

  1. The highest valency of the element Z is six.
  2. The formula of the fluoride of Z will be ZF6.

Solution 13:
The three valencies of element are-

  1. Two-Since the element X combines with two hydrogen to form H2X and two atoms of X combines with one carbon to form CX2.
  2. Four-Since the element X combines with two oxygen to form XO2.
  3. Six-Since the element X combines with three oxygen to form XO3.

Solution 14:
Variable valency – Some elements are capable of showing more than one valency in their compounds called variable valency.
Some elements show variable valency i.e. more than one valency since these elements have more than one common valency state.

Solution 15:
Chemical formula – It represents the composition of a molecule of the substance in terms of the symbols of the elements present in the molecule. The rule for writing the formula is criss-cross method.

  1. The positive and negative radicals are represented by their symbols and written side by side with the correct valency written below each.
  2. The valencies are divided by their highest common factor if any to get the simplest ratio.
  3. These numbers are then interchanged and written as subscripts.

Solution 16:
Frank ICSE Solutions for Class 9 Chemistry - The Language of Chemistry 3

Solution 17:

  1. Sodium hydrogencarbonate
  2. Sodium hexacyanoferrate(III)
  3. Manganese(II) borate
  4. Calcium phosphate
  5. Potassium manganate(VI)

Solution 18:
Co stands for cobalt which is an element while CO stands for carbon monoxide which is a compound.

Solution 19:
Radical – A radical is an atom or a group of atoms of same or different elements that behaves in the manner of positive or negative ion. Radicals have their own combining power(valency) and chemical formulae.
Examples-
Monovalent  radicals -H–,OH–,Cl–,NO3–,H+,Na+,K+,NH4+
Trivalent radicals-PO43- ,Fe(CN)63-,AsO3 3-,N3-,Fe3+,Al3+,Bi3+,Au3+

Solution 20:
Frank ICSE Solutions for Class 9 Chemistry - The Language of Chemistry 4

Solution 21:

  1. Anion – Negatively charged radicals are termed as anions.
  2. Cation – Positively charged radicals are termed as cations.

Solution 22:
Disadvantages associated with hit and trial method of balancing of equations-

  1. It is tedious and takes a long time.
  2. The method is rather difficult for balancing such equations which contain the same element being repeated in a number of compounds.
  3. It does not give any information regarding the mechanism of the reaction.

ChemistryBiologyPhysicsMaths

Frank ICSE Solutions for Class 9 Chemistry – Physical and chemical changes

by

Frank ICSE Solutions for Class 9 Chemistry – Physical and chemical changes

PAGE NO :74
Solution 1:
A physical change is a temporary change in which no new substance is formed and the composition or identity of the substance is not altered although certain specific physical properties may be changed.

Solution 2:
A chemical change is a permanent change in which the original substance gives rise to one or more substances with different properties.

Solution 3:
The reactions in which heat is evolved are called exothermic reactions while the reactions in which heat is absorbed are called endothermic reactions.

Solution 4:

  1. False
  2. False
  3. False
  4. False
  5. True

Solution 5:
Frank ICSE Solutions for Class 9 Chemistry - Physical and chemical changes 1

Solution 6:
Possible conditions for a chemical change are-

  1. One or more new substance is formed during reaction.
  2. The change occurring during the reaction is permanent.
  3. The mass of the substance undergoing a chemical change is generally altered.
  4. Chemical change involves  making and breaking of bond.

Solution 7:
Frank ICSE Solutions for Class 9 Chemistry - Physical and chemical changes 2

Solution 8:

(a) Redox reaction – The reaction in which both oxidation and reduction takes place simultaneously is known as rtedox reaction. Oxidation is a reaction that involves the addition of oxygen or the removal of the hydrogen. Reduction is a reaction that involves the addition of hydrogen or the removal of oxygen.
Frank ICSE Solutions for Class 9 Chemistry - Physical and chemical changes 3
(b) Oxidation – Oxidation is a reaction that involves the addition of oxygen or the removal of the hydrogen. In electronic concept, it is defined as the process in which an atom, molecule or ion loses one or more electrons. This results in increase in the positive charge or decrease in negative charge on the resulting species.
Frank ICSE Solutions for Class 9 Chemistry - Physical and chemical changes 4
(c) Reduction – Reduction is a reaction that involves the addition of hydrogen or the removal of oxygen. In the electronic concept, it is defined as the process in which an atom, molecule or ion gains one or more electrons. This results in increase in the negative  charge or decrease in positive charge on the resulting species.
Frank ICSE Solutions for Class 9 Chemistry - Physical and chemical changes 5

Solution 9:

  1. Exothermic reaction
  2. Endothermic reaction

Solution 10:
Frank ICSE Solutions for Class 9 Chemistry - Physical and chemical changes 6

Solution 11:
The chemical reactions which occur with the absorption of light energy are called photochemical reactions.
Examples-
Decomposition of silver nitrate takes place in the presence of light.
Frank ICSE Solutions for Class 9 Chemistry - Physical and chemical changes 7

Solution 12:
As the burning substance combines with oxygen ,the total mass of the products should be greater than that of the burning substance. For example,when,magnesium is burnt,a new substance magnesium oxide is formed,whose weight is greater than that of the original magnesium.
Experiment – A crucible is weighed containing about 0.5 gm of magnesium.Now crucible is heated.When magnesium begins to burn,the lid is put back on the crucible and the lid is occasionally raised to allow air to enter and burn the magnesium such that no product is lost.When,all the magnesium has been burnt up, the crucible is allowed to cool and then on weighing it  we observe that there is gain in weight.

Solution 13:
Frank ICSE Solutions for Class 9 Chemistry - Physical and chemical changes 8

Solution 14:
Three conditions necessary for burning are-

  1. The substance to be burnt must be combustible.
  2. A supporter of combustion such as air or oxygen must be present.
  3. A combustible substance must be heated to its ignition temperature.

PAGE NO :75
Solution 15:
Frank ICSE Solutions for Class 9 Chemistry - Physical and chemical changes 9

Solution 16:
Frank ICSE Solutions for Class 9 Chemistry - Physical and chemical changes 10

Solution 17:
When oxidation occurs there is a loss of electrons but simultaneously there is a gain of electrons by other species which is called reduction. These both process occur simultaneously so we can say that both oxidation and reduction go hand in hand and such reactions are known as redox reaction.

Solution 18:

  1. Copper is oxidized to copper sulphate while sulphur in sulphuric acid is reduced to sulphur dioxide.
  2. Silver in silver oxide is reduced to silver while oxygen in hydrogen peroxide is oxidised to molecular oxygen.

Solution 19:
Frank ICSE Solutions for Class 9 Chemistry - Physical and chemical changes 11
Frank ICSE Solutions for Class 9 Chemistry - Physical and chemical changes 12

Solution 20:
Frank ICSE Solutions for Class 9 Chemistry - Physical and chemical changes 13

Solution 21:
A candle is a stick of paraffin wax with cotton wick.As a candle burns wax melts and trickles down. It gets solidified shortly. This is physical change. Paraffin wax is a mixture of hydrocarbons. When wick catches fire, paraffin wax melts, evaporates and burns in air like any hydrocarbon to give carbon dioxide and water. This is a chemical change.

Solution 22:

  1. physical
  2. chemical
  3. chemical
  4. physical

Solution 23:
Two examples are:-

  1. Burning of wood-carbon get oxidized and oxygen gets reduced.
  2. Rusting-In it iron is oxidized.

Solution 24:

  1. Chromium(VI) .
  2. Hydrogen peroxide
  3. Barium carbonate.
  4. Silver nitrate.
  5. Manganese dioxide.

Solution 25:
Ignition temperature – Ignition temperature is the lowest temperature up to which temperature of a substance must be raised so that it catches fire.
A combustible substance must be heated to its ignition temperature for burning.

Solution 26:
Frank ICSE Solutions for Class 9 Chemistry - Physical and chemical changes 14

Solution 27:
On heating few crystals of iodine in a test tube, the grey crystals sublimes and dense violet fumes are seen. On cooling, the vapours again form the crystals. So, a physical change can be reversed.

Solution 28:
Frank ICSE Solutions for Class 9 Chemistry - Physical and chemical changes 20

Solution 29:
When water is freezed and evaporated, these both are physical changes because-

  1. The change is temporary and reversible.
  2. No new substance is formed and the chemical composition of the original substance remains the same.
  3. Mass of the substance remains unchanged
  4. The amount of energy required to bring about a physical change is generally equal to the amount of energy required to reverse the change. Hence,there is no net energy change involved.

Solution 30:
Frank ICSE Solutions for Class 9 Chemistry - Physical and chemical changes 15

Solution 31:
Air is necessary for burning. Incorrect amount of air in fuel combustion accounts for the largest losses in combustion system. If the fuel does not get enough air for combustion it will generate smoke and a potentially unhealthy mixture of gas products.

Solution 32:

  1. (a) Combustible substances -The substances that catch fire and burn easily. Ex-Wood, Charcoal, petrol, kerosene etc.
    Non-combustible substances-Substance which cannot burn in air or oxygen are called as non- combustible substances. Ex-Nitrogen gas, carbon dioxide etc.
  2. (b) Two substances other than oxygen that support combustion are-
    1. Hydrogen
    2. Nitrogen

Solution 33:

  1. (a)
    1. Burning of coal in air releases CO2 in air.
    2. Respiration releases carbon dioxide and water vapours.
  2. (b)
    1. Photosynthesis removes CO2 from the atmosphere. Plants take carbon dioxide from the atmosphere in the presence of sunlight and use it to synthesise glucose with the liberation of oxygen.
    2. Some man made chemical activities such as setting of mortar also use atmospheric carbon dioxide and helps in removing carbon dioxide.

Solution 34:
Nitrogen is inert in nature and does not support combustion while oxygen supports combustion.If proportions of nitrogen and oxygen in the air were reversed then the rate of combustion of substances will increase.

Solution 35:
Heating of sulphur – If some powdered sulphur is heated gently in a glass test tube, it melts to a pale yellow liquid. Flame is removed to stop heating, it is quickly changed back to solid sulphur.

PAGE NO :76
Solution 36:
Activity series – The arrangement of the metals in the decreasing order of their chemical reactivity is called the activity series.
In displacement reactions, a more reactive element (metal or non-metal) displaces a lesser reactive element from its compound. With the help of the activity series, it is possible to predict which metals will displace other metals from their solutions.

Solution 37:
Balance of oxygen and carbon dioxide is maintained in nature because there is a natural oxygen cycle and a natural carbon cycle operating all the time by which the desired proportions of the two gases in the air are maintained. This is also known as carbon dioxide-oxygen cycle.
Frank ICSE Solutions for Class 9 Chemistry - Physical and chemical changes 16

Solution 38:
Frank ICSE Solutions for Class 9 Chemistry - Physical and chemical changes 17

Solution 39:
Carbon dioxide from the atmosphere enters the plant through photosynthesis, where carbohydrates are produced. From green plants, the carbon in the form of carbohydrates, etc. enter the animal and human bodies. The atmospheric carbon dioxide gets dissolved in oceans by diffusion. Marine algae and photosynthetic bacteria obtain carbon dioxide from water.
Carbon dioxide returns to the atmosphere by respiration, combustion of fossil fuels like coal, wood, petroleum etc., weathering of rocks, volcanic eruptions etc.
Frank ICSE Solutions for Class 9 Chemistry - Physical and chemical changes 18

Solution 40:
Frank ICSE Solutions for Class 9 Chemistry - Physical and chemical changes 18

ChemistryBiologyPhysicsMaths

Frank ICSE Solutions for Class 9 Chemistry – Water

by

Frank ICSE Solutions for Class 9 Chemistry – Water

PAGE NO :96
Solution 1:
The molecular formula of water is H2O, this shows that water is not an element but it is a compound made up of two elements hydrogen and oxygen  combined in a fixed ratio, i.e., 1:8 by mass. This also shows that the properties of water is totally different from those of hydrogen and oxygen as compounds have completely different properties than the elements of which it is made up of.

Solution 2:
Two characteristics properties responsible for making water a good solvent are:

  1. Water molecule can form hydrogen bonds with the molecules of other compounds.
  2. Water molecule is polar in nature.

Solution 3:
Frank ICSE Solutions for Class 9 Chemistry - Water 1

Solution 4:

  1. (a) Physical properties of water:
    1. Pure water is colourless, transparent, odourless and tasteless liquid.
    2. Boiling and Freezing points: At normal atmospheric pressure water boils at 100oC and freezes at 0oC.
    3. Pure water being a covalent compound is a very poor conductor of heat and electricity.On addition of electrolytes it becomes a good conductor of heat and electricity.
    4. Solvent properties:Water is a remarkable solvent dissolves many substances forming aqueous solutions because of its high dielectric constant.
    5. Anomalous behavior: On cooling water contracts in volume, as do other liquids, but at 4o C, it starts expanding, and continues to do till the temperature reaches 0oC,the point at which it converts to ice.
  2. (b)
    1. Boiling point of water: It increases with the addition of salt in water.
    2. Freezing point of water: It decreases with the addition of salt in water.
    3. Density of water: It increases with the addition of salt in water.

Solution 5:
Due to its high specific heat capacity, water is used in cooling systems for e.g., as coolant in motor car radiators.

Solution 6:
Frank ICSE Solutions for Class 9 Chemistry - Water 2

Solution 7:

  1. (a) Water reacts with metals oxides: corresponding hydroxides are formed which act as alkalis.
  2. (b) Water reacts with non metals oxides: corresponding acids are formed.

Solution 8:
Frank ICSE Solutions for Class 9 Chemistry - Water 3

Solution 9:
We can test the odourless, colourless liquid by:

  1. Measuring its boiling point, if comes out to be 100 oC then it confirms the liquid to be water.
  2. Measuring its melting point, if comes out to be 0 oC then it confirms the liquid to be water.

Solution 10:
Frank ICSE Solutions for Class 9 Chemistry - Water 4

Solution 11:

  1. (a) Water being the universal solvent ,acts as an important mode of transport in plants,also water taken from natural source contains dissolved salts in them which is essential for the growth and development of plants
  2. (b) Water constitutes 3/4th of our human body and it is necessary for the survival of human beings and being the universal solvent helps in transportation and also regulates the body temperature.It also contains dissolved salts which supply essential minerals which are necessary for our body.

Solution 12:
Frank ICSE Solutions for Class 9 Chemistry - Water 5

Solution 13:
Frank ICSE Solutions for Class 9 Chemistry - Water 6

Solution 14:
Density of water is 0.997 gcm-3 at 4oC . The density of water decreases when the temperature increases above 4oC or decreases below 4oC.
At 40C, water has its maximum density and minimum volume. At any temperatur above or below 4 C, the density of water decreases. This property is called anomalous expansion of water. The significance of this unique property of water is that it enables marine life to exist in the colder regions of the world, because even when water freezes on the top, it is still liquid below the ice layer.

Solution 15:
At 40C, water has its maximum density and minimum volume. The property of anomalous expansion of water enables marine life to exist in the colder regions of the world because even when water freezes on the top, it is still liquid below the ice layer.

PAGE NO :97
Solution 16:
Frank ICSE Solutions for Class 9 Chemistry - Water 11

Solution 17:
Frank ICSE Solutions for Class 9 Chemistry - Water 7

Solution 18:

  1. (a) Liquids: alcohols, acids
  2. (b) Solids: Sugar, urea
  3. (c) Gases: Oxygen, carbon dioxide

Solution 19:
Rain water is the purest form of natural water.

Solution 20:

  1. (a) Solid in a liquid: Solubility decreases with rise in temperature in an exothermic process, for example, calcium sulphate(CaSO4), sodium sulphate(NaSO4), and in an endothermic reaction solubility increases with rise in temperature,for example potassium nitrte(KNO3) and sodium nitrate(NaNO3).
  2. (b) A gas in a liquid: Solubility decreases with rise in temperature.Thus, gases dissolves readily in cold water than in hot water.

Solution 21:
Frank ICSE Solutions for Class 9 Chemistry - Water 8

Solution 22:

  1. (a) Density of water is 0.997 gcm-3 at 4oC .The density of water decreases when the temperature decreases below 4oC. So ice has less density of 0.92 and is lighter  then that of water hence it floats on water.
  2. (b) A solution is said to be saturated if at a particular temperature if no more of the solute can be dissolved in it at that temperature, when the temperature is increased more solute particles can be dissolved in that saturated solution as the solubility of most of the substances generally increases with rise in temperature and thereby making it unsaturated.
  3. (c) Solubility of gases decreases with increase in temperature hence hot water contains less dissolved air than cold water.

Solution 23:

  1. (a) Solute: The substance which dissolves in a medium to produce a solution is called the solute.
  2. (b) Solvent: It is the medium in which the solute dissolves.
  3. (c) Solution: A homogeneous mixture that has a uniform composition throughout the volume of the mixture. It is the medium in which the solute dissolves.

Solution 24:

  1. (a) When we heat a saturated solution more solute can be dissolved in it, it as mostly solubility increases on raising the temperature and the solution then becomes an unsaturated solution.
  2. (b) When a hot saturated solution is cooled slowly and is kept undisturbed the excess salt does not separates out . Thus the solution becomes a supersaturated solution which contains more solute in it than it can hold at room temperature.
  3. (c) When the quantity of solvent increases,greater amount of solute can be dissolved.

Solution 25:
Frank ICSE Solutions for Class 9 Chemistry - Water 9

Solution 26:
Frank ICSE Solutions for Class 9 Chemistry - Water 10

Solution 27:
Solubility of a solid depends on:

  1. Size of particles: Smaller the size of particles of the solute, greater is the solubility.
  2. Contact between solute and the solvent: Increased contact between the solute and the solvent increases the solubility.
  3. Temperature: The variation of solubility with temperature depends on its nature i.e. whether the reaction is exothermic or endothermic.
    For exothermic reactions-The solubility decreases on increasing the temperature.
    For endothermic reaction-The solubility increases on increasing the temperature.

Solution 28:
Henry’s law states that:
At a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.

Solution 29:

  1. Z is least reactive so it will be found free in nature.
  2. X is more reactive so it will react with oxygen more readily and with ease.
  3. Z
  4.  Y is iron whose oxide is brown coloured Fe2O3.
  5. X
  6. The piece of Y i.e., iron is more reactive then copper so it will displace copper from copper nitrate and a brown layer of copper will be developed on the iron piece.

Solution 30:
Drop in, a crystal of the solute that is in the solution. If the crystal dissolves its unsaturated, if it stays the same size then its saturated and if it gets bigger than its supersaturated.

  1. This is because an unsaturated solution will be able to take in more solute, so it dissolves the crystal.
  2. A saturated solution will not take in more solute but will also not deposit any solute so the crystal stays the same size.
  3. A supersaturated solution wants to deposit its excess solute and become saturated, it just needs something to start it along.

The crystal starts it up and it will deposit its excess solute onto the crystal making the crystal bigger.

PAGE NO :98
Solution 31:

  1. (a) Increase in weight: when sodium chloride when exposed in air it gains moisture and its weight increases.
  2. (b) Decrease in weight: iron when exposed to air gets rusted due to the presence of moisture in the air it gets corroded, and hence its weight is reduced.
  3. (c) No effect on weight: when conc. Sulphuric acid when exposed to air  does not react and no change occurs in weight.

Solution 32:
Water pollution may be defined as the contamination of water by foreign substances which make it harmful for health of animals or plants or aquatic life, make it unfit for drinking and for domestic, industrial and agriculture use.

Solution 33:
Major pollutants of water are:
Ground water pollutants: Septic tanks, industry by products like pesticides, fertilizers, tanneries, mining wastes.
Surface water pollutants: No. of gases present in atmosphere like SO2, CO2, H2S, NOx, CO, etc., pollute surface water.
Lake water pollutant: organic wastes from hills, toxic effluents from urban areas, industrial effluents, dumping of huge amounts of sediments etc.,
River water pollutants: Industrial discharge, sewage discharges, detergents, discharges from drug, paper, and textile industries
Marine water pollutant: major pollutant is oil spills.

Solution 34:
Various sources of water pollution are:

  1. Natural process: Washing away of decomposed and animal wastes into main stream of water.
  2. Human activity: 
    1. (a)Discharge of Household detergents:  detergents used as a cleaning agent produce foam and pollute water. They do not undergo bio-degradation.
    2. (b) Discharge of industrial effluents: Industrial activities generate a variety of waste products which are generally discharged into water streams.The pollutants associated with the industrial effluents are  organic matter, inorganic dissolved salts, suspended solids. They inhibit oxidation or organic compounds; stabilize the colloidal impurities which do not aggregate to settle down.
    3. (c) Sewage:  Sewage is cloudy dilute aqueous solution containing minerals and organic matter.Sewage from homes and industries contains decomposable organic matter ,inorganic cations and anions,toxic metals etc.Pouring the drains and sewers in fresh water bodies causes water pollution.
      Water pollution due to sewage creates the following problems:

      1. Self purifying ability of water is lost and it becomes unfit for domestic purpose.
      2. Self regulatory capabilities of aquatic organism is retarded.
      3. Sewages produce pathogens which are diseases causing bacteria and result in water born gastro-intestinal diseases.

Solution 35:
Water treated for safe effluents involves sequential treatment:

  1. Primary treatment: The primary treatment involves physico-chemical processes to reduce settle able suspended solids of the wastes water and smoothened out individual effluent flow variations.It involves physic-chemical processes such as sedimentation,aeration,adsorption,oxidation etc.
  2. Secondary treatment: In this, the dissolved and colloidal organic matter present in waste is removed by biological processes involving bacteria and other micro organisms.
    These process may be aerobic or anaerobic.
    Aerobic treatment: Purification is carried out by aerobes in the presence of molecular oxygen.
    Anaerobic treatment: Purification of waste is achieved by anaerobes in complete absence of molecular oxygen.
  3. Tertiary treatment: It is the final treatment for polishing the effluents from secondary treatment. By this process suspended solids are removed, bacteria are removed, and organic and inorganic solids are removed.

Solution 36:
Two water born diseases are:

  1. Gastroenteritis
  2. Bacterial dysentery

ChemistryBiologyPhysicsMaths

Frank ICSE Solutions for Class 9 Chemistry – Atomic Structure

by

Frank ICSE Solutions for Class 9 Chemistry – Atomic Structure

PAGE NO :113
Solution 1:
Frank ICSE Solutions for Class 9 Chemistry - Atomic Structure 1

Solution 2:
Frank ICSE Solutions for Class 9 Chemistry - Atomic Structure 2

Solution 3:

  1. (a) Mass of an atom – Protons and neutrons
  2. (b) Size of an atom – Electrons

Solution 4:

Three fundamental particles of an atom are-

  1. Proton
  2. Electron
  3. Neutron

Solution 5:

  1. (a) An atom – An atom is the smallest particle of an element which may or may not be capable of independent existence.
  2. (b) An element – An element is usually defined as a pure substance that contains only one kind of particles. These particles may be atoms or molecules.

Solution 6:
Atomic number – The number of protons present in the nucleus of an atom is called the atomic number of the atom.
It is denoted by ‘Z’.

Solution 7:
The protons and neutrons are collectively called as nucleons.

Solution 8:
Isotopes are atoms of the same element, having the same atomic number, same chemical properties but different mass number, i.e., the atoms differ in the number of neutrons. The three isotopes of hydrogen atoms are-

  1. Protium
  2. Deuterium
  3. Tritium

Solution 9:
Electrons take part in a chemical reaction. Therefore, the chemical properties of an element depend upon the electronic configuration. Since, isotopes of an element have the same atomic number and hence same electronic configuration. So, they exhibit the same chemical properties.

Solution 10:
Frank ICSE Solutions for Class 9 Chemistry - Atomic Structure 3

Solution 11:
The outermost orbit of an element is called valence shell. The electrons present in the outermost orbit (valence shell) of an element are called valence electrons.

Solution 12:
Atoms may have incomplete octet. During the formation of a molecule, an atom of a particular element gains, loses or shares electrons until it acquires a stable configuration of eight electrons in its valence shell.

Solution 13:

  1. (a) Atomic number = Number of protons = 20
  2. (b) Mass number = Number of protons +Number of electrons = 20 + 20 = 40
  3. (c) Electronic configuration = 2, 8, 8, 2
  4. (d) Valency = 2

Solution 14:

  1. (a) A=1
    B=3
    C=2
    D=1
    E=1
  2. (b) E contains the greatest number of neutrons.
  3. (c) A contains the least number of electrons.
  4. (d) B contains equal number of electrons and neutrons.
  5. (e) A is a metal.
  6. (f) Fluorine is the most reactive of the non-metals.
  7. (g) Both are electronegative and non-metals.
  8. (h) D and E belongs to a particular family.
  9. (i) A3B will be the formula if atoms of A combines with atoms of B.
  10. (j) ‘B’ will combine in  a trivalent  element while ‘C’ will combine as a bivalent element.

PAGE NO :114
Solution 15:
“During the formation of the molecule, an atom of a particular element gains, loses electrons or shares electrons until it acquires a stable configuration of eight electrons in its valence shell” i.e. until it acquires octet.

Solution 16:
K can accommodate maximum of 2 electrons.
L can accommodate maximum of 8 electrons.
M can accommodate maximum of 18 electrons.

Solution 17:
Cathode rays are formed at the negative electrode of the discharge tube experiment.

Solution 18:

  1. In K maximum number of 2 electrons can be accommodated.
  2. In L maximum number of 8 electrons can be accommodated.
  3. In M maximum number of 18 electrons can be accommodated.
  4. In N maximum number of 32 electrons can be accommodated.

Solution 19:
Frank ICSE Solutions for Class 9 Chemistry - Atomic Structure 4

Solution 20:
Electronic configuration of magnesium is -2, 8, 2. Since, it has 2 electrons in its valence shell, so its valency is 2.

Solution 21:
Number of electrons in Sodium = 11
Number of protons in sodium = 11
Number of neutrons in sodium = 12
Number of nucleons in sodium = 23

Solution 22:
Inert elements are the elements which have completely filled valence shell. Since, they are already stable and do not need more electrons, they do not combine with other atoms. So, they exist as monoatoms in molecule.

Solution 23:

  1. (a) Hydrogen
  2. (b) K shell.
  3. (c) Magnesium
  4. (d) Isotopes
  5. (e) Helium has zero valency.

Solution 24:

  1. (a) The number of protons = 9
  2. (b) The number of neutrons = 19 – 9 = 10
  3. (c) The number of electrons = 9

Solution 25:
Atomic number is the number of protons of an atom which is unique to an atom but mass number is the total of number of protons and number of neutrons which may or may not be same to other atoms since there is probability of combination of number of protons and number of neutrons be same for two atoms.

ChemistryBiologyPhysicsMaths

Frank ICSE Solutions for Class 9 Chemistry – Study of the First Element – Hydrogen

by

Frank ICSE Solutions for Class 9 Chemistry – Study of the First Element – Hydrogen

PAGE NO :146
Solution 1:

  1. (a) Symbol of hydrogen is ‘H’ and its molecular formula is H2.
  2. (b) 2 H means 2 atoms of hydrogen while H2 means one molecule of hydrogen.
  3. (c) Lavoisier gave “Hydrogen” its name because it means water product.

Solution 2:
Hydrogen is found in free state as well as in combined  state.

  1. In free state, it is found in traces in the earth’s crust and atmosphere. On the sun and bright stars, hydrogen is very abundant.It is suggested that the source of sun’s energy is fusion of hydrogen to helium.
  2. In combined state it is found in the compounds like water, acids, organic materials and minerals. Natural gas coming out from oil wells, coal mines and volcanoes invariably contains this gas.

Solution 3:
Hydrogen resembles the alkali in following manner-

  1. Electronic configuration – Hydrogen as well as alkali metals have one electron in their valence shell.
    H (1) = 1      ; Li(3)= 2, 1   ; Na(11) =2, 8, 1
  2. Ion formation – Hydrogen loses one electron to form H+ ion like the alkali metals which form Li+, Na+, K+ etc.
  3. Valency electrons – Like alkali metals, hydrogen exhibit valency of one in its compounds , as it has only one electron in its outermost shell.
  4. Combination with non-metals – Like alkali metals, hydrogen combines with non-metals such as oxygen, chlorine and sulphur forming their oxides, chlorides and sulphides respectively.
  5. Reducing action – Like alkali metals, hydrogen is also a very good reducing agent.

Solution 4:
Hydrogen resembles the alkali in following manner-

  1. Electronic configuration – All the halogens have seven electrons in their outermost shell and need just one more electron to attain stable inert gas configuration. Similarly, hydrogen with one electron in its outermost shell requires one electron to attain a stable inert gas(Helium) configuration.
  2. Valency – Hydrogen and halogen both show a valency of one.
  3. Non-metals – Hydrogen is non-metallic like halogen.
  4. Atomicity – Hydrogen as well as halogens are diatomic gases, e.g.H2,Cl2.Br2 etc.
  5. Ion formation – Halogens have a strong tendency to gain an electron to form halide ions.In similar way, hydrogen shows tendency to gain one electron to form hydride ion (H–).

Solution 5:
Frank ICSE Solutions for Class 9 Chemistry - Study of the First Element - Hydrogen 1

Solution 6:
Frank ICSE Solutions for Class 9 Chemistry - Study of the First Element - Hydrogen 2

Solution 7:
Frank ICSE Solutions for Class 9 Chemistry - Study of the First Element - Hydrogen 3

Solution 8:
Hydrogen gas  obtained in the laboratory by dilute H2SO4 and granulated zinc have following impurities-

  1. Hydrogen sulphide (H2S),
  2. Sulphur dioxide (SO2),
  3. Oxides of nitrogen,
  4. Phosphine (PH3),
  5. Arsine (AsH3),
  6. Carbon dioxide, Nitrogen oxides,
  7. Water vapour
    They are removed by passing through-

    1. Lead nitrate solution-It absorbs H2S.
    2. Silver nitrate solution (AgNO3)-It absorbs PH3, AsH3
    3. Caustic potash (solid KOH)-It absorbs CO2, SO2, oxides of nitrogen
    4. Anhydrous calcium chloride or P2O5-It absorbs moisture.

Solution 9:
Frank ICSE Solutions for Class 9 Chemistry - Study of the First Element - Hydrogen 4

Solution 10:
Frank ICSE Solutions for Class 9 Chemistry - Study of the First Element - Hydrogen 5
Frank ICSE Solutions for Class 9 Chemistry - Study of the First Element - Hydrogen 6

PAGE NO :147
Solution 11:
Frank ICSE Solutions for Class 9 Chemistry - Study of the First Element - Hydrogen 7

Solution 12:
Frank ICSE Solutions for Class 9 Chemistry - Study of the First Element - Hydrogen 8

Solution 13:

  1. (a) Nickel, hydrogen
  2. (b) above, dilute mineral
  3. (c) covalent, electronegative
  4. (d) CuO, hydrogen, water
  5. (e) CO, H2
  6. (f) alkali
  7. (g) nascent hydrogen
  8. (h) water

Solution 14:

  1. (a) False
  2. (b) False
  3. (c) True
  4. (d) True
  5. (e) True
  6. (f) True
  7. (g) True
  8. (h) False

Solution 15:
Frank ICSE Solutions for Class 9 Chemistry - Study of the First Element - Hydrogen 9
Frank ICSE Solutions for Class 9 Chemistry - Study of the First Element - Hydrogen 10

PAGE NO :148
Solution 16:
Frank ICSE Solutions for Class 9 Chemistry - Study of the First Element - Hydrogen 11

Solution 17:
Frank ICSE Solutions for Class 9 Chemistry - Study of the First Element - Hydrogen 12

Solution 18:
Frank ICSE Solutions for Class 9 Chemistry - Study of the First Element - Hydrogen 14

Solution 19:
Some pieces of zinc granules are placed in Woulfe’s bottle and the apparatus is made in air tight. Now dilute sulphuric acid is poured through the thistle funnel.
Observation: The reaction takes place at room temperature even without heating. A brisk effervescence with the evolution of gas is seen inside the bottle.
If burning candle is brought near the bubbles of hydrogen gas, they explode.This proves that bubbles were full of hydrogen gas and they move up in the air because they are lighter than air.

Solution 20:

  1. (a) Meteorological balloons – The low density and high lifting power of hydrogen made it useful in meteorological balloons used for studying air currents and weather conditions. However, due to its highly inflammable nature it has been replaced by helium which has a lifting only slightly less than that of hydrogen.
  2. (b) In metallurgy – Hydrogen acts as a very good reducing agent. It is used to obtain metals by reducing their oxides.
  3. (c) In fuel – Hydrogen has very high heat of combustions, therefore it is used as fuel  in the form of coal gas, water gas and liquid hydrogen(for rocket propulsion).
  4. (d) In making fertilizers – A large quantity of hydrogen is used in the manufacture of ammonia by Haber process. Ammonia is used in manufacture of HCl and methyl alcohol.

Solution 21:
Frank ICSE Solutions for Class 9 Chemistry - Study of the First Element - Hydrogen 15

ChemistryBiologyPhysicsMaths