ICSE Class 9 Chemistry Sample Question Paper 8 with Answers

ICSE Class 9 Chemistry Sample Question Paper 8 with Answers

Section -1
(Attempt all questions from this section)

Question 1.
(a) Fill in the blanks with the correct choice given in brackets.
(i) Nitric oxide is toxic. …………… [less/more]
(ii) The gaseous material which envelopes the earth is called …………….[atmosphere/ air]
(iii) The lowest region of the atmosphere is called …………………. [troposphere/ stratosphere]
(iv) The stratosphere mainly contains ………… oxygen and ozone.[nitrogen/hydrogen]
(v) Rain water containing H2SO4 and HNO3 is called [acid rain/normal rain]
Answer:
(i) Less
(ii) Atmosphere
(iii) Troposphere
(iv) Nitrogen
(v) Acid rain

ICSE Class 9 Chemistry Sample Question Paper 8 with Answers

(b) Choose the correct answer from the options given below :
(i) Noble gases are :
(A) Monoatomic
(B) Diatomic
(C) Triatomic
(D) None of the above
Answer:
(A) Monoatomic

(ii) Metals below …………. do not rust easily :
(A) Hydrogen
(B) Copper
(C) Potassium
(D) Sodium
Answer:
(B) Copper

(iii) From which of the following metals hydrogen can be prepared :
(A) Copper
(B) Mercury
(C) Both A and B
(D) None of the above
Answer:
(C) Both A and B

ICSE Class 9 Chemistry Sample Question Paper 8 with Answers

(iv) What is the chemical name of bleaching powder ?
(A) Calcium oxychloride
(B) Calcium hypochlorite
(C) Calcium hydroxide
(D) Both A and B
Answer:
(D) Both A and B

(v) Which of the following conditions are true regarding gases ?
(A) Gases exert pressure in all directions.
(B) Gases are not compressible.
(C) Gases have low density.
(D) Both A and C.
Answer:
(D) Both A and C.

ICSE Class 9 Chemistry Sample Question Paper 8 with Answers

(c) List the major health effects of the following pollutants.
(i) Carbon monoxide
(ii) Suspended particulate matter
(iii) Ozone
(iv) CFC
(v) Oxides of nitrogen
Answer:
(i) Reduces oxygen in blood causing retardation and dizziness.
(ii) Small particles get lodged in the lungs and gradually damage the functioning of lungs.
(iii) Burning, etching, watery eyes and lowered resistance to repiratory disease.
(iv) Reduces ozone layer that protects us from the harmful ultraviolet rays of the sun.
(v) Smog produces acid rain that makes children more susceptible to respiratory diseases.

(d) Give reason for each of the following :
(i) Why hydrogen cannot be collected by the downward displacement of air ?
(ii) Why nitric acid cannot be used in the preparation of hydrogen ?
(iii) Why rain water and distilled water do not form concentric rings ?
(iv) Why distilled water when kept in a sealed bottle for a long time leaves etchings on the inside surface of glass ?
(v) Why a salt formed due to a strong base and a weak acid, on dissolving in water, will make a basic solution
Answer:
(i) Hydrogen cannot be collected by the downward displacement of air because it forms an explosive mixture with air.

ICSE Class 9 Chemistry Sample Question Paper 8 with Answers

(ii) Nitric acid cannot be used in the preparation of hydrogen because it is a powerful oxidizing agent, and the oxygen formed due to its decomposition oxidizes the hydrogen to give water, thus defeating the purpose of the reaction.

(iii) Rain water and distilled water do not contain dissolved solids this is the reason they do not form concentric rings.

(iv) Substances that are apparently insoluble in water actually dissolve in it in traces. When distilled water is kept in a glass it dissolves in water and leaves etchings on the inside surface of the glass.

(v) This happens because of hydrolysis, it is a process in which a salt and water react to form an acidic or a basic solution. In this process only those salts hydrolyze that are formed by the reaction of strong base and weak acid and strong acid and weak base.

(e) What do you observe when :
(i) When methane undergoes combustion ?
(ii) When CuSO4.5H2O is treated with cone, sulphuric acid.
(iii) When ammonium dichromate is heated ?
(iv) When cone. HCl is added to oxidizing agents like Pb3O4, MnO2 ?
(v) When carbon monoxide is treated with platinum ?
Answer:
(i) Combustion of natural gas is an important source of energy for homes and industry,when methane (natural gas) undergoes combustion large amount of energy is produced which is used in the form of fuels in vehicles.

(ii) When CuSO4.5H2O is treated with cone. H2SO4, then dehydration takes place and cone, sulphuric acid removes water molecules from blue vitriol.

ICSE Class 9 Chemistry Sample Question Paper 8 with Answers

(iii) When ammonium dichromate is heated it swells up and decomposes violently with flashes of light leaving greenish residue, water vapour and nitrogen is evolved during this reaction.

(iv) When cone. HCl is added to oxidizing agents like Pb3O4, MnO2 it turns moist blue litmus paper red and finally bleaches i.e., decolourizes it.

(v) Carbon monoxide changes into carbon dioxide in the presence of finely divided platinum as catalyst.

(f) Answer the following questions :
(i) What is diffusion ?
(ii) What are the gas laws and write down its standard variables ?
(iii) State Charle’s law in terms of dry gas
Answer:
(i) Diffusion is the process of gradual mixing of two substances, kept in contact, by molecular motion. Inter-particle spaces in a gas are very large. When two gases are brought in contact with each other, their molecules mix with each other in such a manner that a homogeneous gaseous mixture is formed.

(ii) The behaviour of gases under known conditions of pressure, volume and temperature is described by gas laws. The physical behaviour of gases can be described by three standard variables :
(a) Volume (V)
(b) Pressure (P)
(c) Temperature (T)

ICSE Class 9 Chemistry Sample Question Paper 8 with Answers

(iii) It says that volume of a given mass of a dry gas is directly proportional to its absolute temperature, if the pressure remains constant.

(g) Write balanced chemical equations : .
(i) 1. Decomposition of copper nitrate.
2. Thermal dissociation of phosphorus penta chloride.
Answer:
1. \(2 \mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2} \stackrel{\Delta}{\longrightarrow} \mathrm{CuO}+4 \mathrm{NO}_{2}+\mathrm{O}_{2}\)
2. \(\mathrm{PCl}_{5} \stackrel{\Delta}{\longrightarrow} \mathrm{PCl}_{3}+\mathrm{Cl}_{2}\)

(ii) 1. Magnesium bums in oxygen.
2. Hydrogen bums in air or oxygen.
3. Carbon dioxide is passed through lime water.
Answer:
1. 2Mg + O2 → 2MgO
2. 2H2 + O2 → 2H2O
3. CO2 + Ca(OH)2 →CaCO3 + H2O

(h) Match Column A with Column B.

Column A Column B
(i) Binary solution
(ii) Silica
(iii) Heat is absorbed
(iv) Sodium chloride
(v) Cathode rays
(A) Endothermic reaction
(B) Electrons
(C) Have high solubi0ty
(D) Has two components
(E) Silicon dioxide

Answer:
(i) (D) (ii) (E) (iii) (A) (iv) (C) (v) (B)

Section II
(Attempt any four questions from this section)

Question 2.
(a) An element ‘M’ has three electrons more than the noble gas. Give the formula of its:
(i) Chloride
(ii) Sulphate
(iii) Hydroxide
(iv) Phosphate
Answer:
The outermost shell of all the noble gases is complete. Thus, its valency is zero. ‘M’ has three electrons more than the noble gas. Thus, the valency of the element ‘M’ is + 3.
(i) MCl3
(ii) M2(SO4)3
(iii) M(OH)3
(iv) MPO4

ICSE Class 9 Chemistry Sample Question Paper 8 with Answers

(b) Complete and balance the following equations :
(i) Cu + HNO3 → ………………….. + ………………. +…………………
(ii) FeSO4 → ……………. + ………………. + SO3
(iii) Pb3O4 + HCl → PbCl2 +………………… +……………….
(iv) H2S + SO2 → ……………….. + ………………
(v) Ca(NO3)2 → CaO + ……………….. + ……………….
(vi) \(\mathrm{Na}_{2} \mathrm{CO}_{3} \cdot 10 \mathrm{H}_{2} \mathrm{O} \stackrel{\text { heat }}{\longrightarrow} \mathrm{Na}_{2} \mathrm{CO}_{3}+10 \mathrm{H}_{2} \mathrm{O}\)
(c) Draw the orbit structure and electron dot diagrams of NaCl, MgCl2 and CaO.
Answer:
ICSE Class 9 Chemistry Sample Question Paper 8 with Answers 1
ICSE Class 9 Chemistry Sample Question Paper 8 with Answers 2
ICSE Class 9 Chemistry Sample Question Paper 8 with Answers 3

Question 3.
(a) (i) Write the process of preparation of hydrogen from zinc.
(ii) Write down two tests for oxidizing agents.
Answer:
(i) Hydrogen can be prepared by action of steam on metals such as zinc. The following reaction occurs :
Zn + H2O → ZnO + H2

1. In the above reaction hydrogen is liberated and zinc is converted to zinc oxide.
2. Zinc is less reactive i.e., it reacts only when it is heated and steam is passed over it.
3. Zinc oxide is yellow when it is hot but white when it is cold.

(ii) Test for oxidizing agents :
1. On heating strongly, they liberate oxygen, which rekindles a glowing splinter.
2. On treating with acidified potassium iodide solution, they liberate iodine, which imparts a blue colour to freshly-prepared starch solution.

ICSE Class 9 Chemistry Sample Question Paper 8 with Answers

(b) What is a periodic table and write down the essential features of Mendeleev’s periodic table ?
Answer:
Periodic table is a chart of elements prepared in such a way that elements with similar properties occur in the same vertical column or group.

Mendeleev’s periodic table contains vertical columns called groups and horizontal rows called periods. Features of his periodic table are as follows :
1. There are in all eight groups i.e., Group I to Group VET Each of these groups from I to VII is divided into two sub-groups : A and B. Group VIII has no sub-group. Inert gases were not known at that time.

2. All elements of a sub-group have similar properties and show the same valency, which is equal to the group number. In a period elements gradually change from metallic to a non-metallic character decreases as one moves from left to right across the horizontal row.

3. In a period, elements gradually change from metallic to non-metallic character or metallic character decreases as one moves from left to right across the horizontal row.

(c) (i) Why is it so that oxides of elements become increasingly basic in character moving in the same direction ?
(ii) State the modified periodic law of Mendeleev.
Answer:
(i) It is on account of gradual increase in metallic character of elements from top to bottom that oxides of elements become increasingly basic in character moving in the same direction. Metallic character increases as one moves down the group.
(ii) The physical and chemical properties of all elements are the periodic function of their atomic numbers.

ICSE Class 9 Chemistry Sample Question Paper 8 with Answers

Question 4.
(a) 16 g of oxygen gas is enclosed in a 1 dm3 flask at 25°C. Calculate the pressure exerted by the gas, if the molecular mass of any gas occupies 22.4 litres at S.T.P.
(b) At what centigrade temperature will the volume of a gas at 0°C triple itself if the pressure remains constant ?
(c) Explain the significance of Boyle’s law and its graphical verification.
Answer:
(a) Oxygen is a diatomic gas.
Its molar mass is 16 x 2 = 32 g
So, 32 g of oxygen occupies 22.4 dm3 at S.T.P.
ICSE Class 9 Chemistry Sample Question Paper 8 with Answers 4
ICSE Class 9 Chemistry Sample Question Paper 8 with Answers 5

(c) Significance of Boyle’s law : On increasing pressure, volume decreases. The gas becomes denser. Thus, at constant temperature, the density of a gas is directly proportional to its pressure. Atmospheric pressure is low at high altitudes, so air is less dense. Hence, a lesser quantity of oxygen is available for breathing. This is the reason why mountaineers have to carry oxygen cylinder with them.

ICSE Class 9 Chemistry Sample Question Paper 8 with Answers

Graphical verification of Boyle’s law :
1. V Vs. \(\frac{1}{\mathrm{P}}\)
Variation in volume (V) plotted against pressure (1/P) at a constant temperature – a straight line passing through the origin is obtained.
ICSE Class 9 Chemistry Sample Question Paper 8 with Answers 6

2. V Vs. P : Variation in volume (V) plotted against pressure (P) at a constant temperature – a hyperbolic curve in the first quadrant is obtained.
ICSE Class 9 Chemistry Sample Question Paper 8 with Answers 7

3. PV Vs. P : Variation in PV plotted against pressure (P) at a constant temperature – a straight line parallel to the X-axis is obtained.
ICSE Class 9 Chemistry Sample Question Paper 8 with Answers 8
Question 5.
(a) (i) What do you mean by isobars ?
(ii) Why are isotopes of an element chemically alike ?
(iii) Why carbon-14 and tritium are known as radio-isotopes ?
Answer:
(a) (i) Isobars are atoms of different elements with the same mass number, but different atomic numbers. Since the properties of elements depend upon atomic number, so they have both different physical and chemical properties.

(ii) As we know that chemical properties are determined by the electronic configuration of an atom. Isotopes have the same atomic number Z i.e., the same number of electrons and proton and hence the same electronic configuration. Thus isotopes of an element are chemically alike.

ICSE Class 9 Chemistry Sample Question Paper 8 with Answers

(iii) Isotopes like tritium, carbon-14 illustrate another difference in physical properties that can occur between isotopes as they are radioactive. The extra neutrons in their nuclei cause them to be unstable so the nuclei break up spontaneously emitting certain types of radiations. Thus carbon-14 and tritium are known as radio-isotopes.

(b) Give reason:
(i) Covalent compounds are insoluble in water but soluble in organic solvents.
(ii) Electrovalent compounds are soluble in water but insoluble in organic solvents.
(iii) Zinc granules are used in the laboratory preparation of hydrogen over pure zinc.
(iv) Name some reducing agents and write the tests for reducing agents.
Answer:
(i) As organic solvents are non-polar, hence, these compounds dissolve in non-polar compounds.
(ii) As water is a polar compound, it decreases the electrostatic forces of attraction, resulting in free ions in aqueous solution. Hence electrostatic compounds dissolve in water.
(iii) It is because the impurity present in granulated zinc is copper, and its catalyzing effect speeds up the rate of reaction.

(c) Name some reducing agents and write the tests for reducing agents.
Answer:
Some examples of reducing agents are as follows :
1. Solids : Carbon, metals like zinc, aluminium, copper and sodium, stannous chloride, glucose etc.
2. Liquids : Hydrogen peroxide, hydrogen iodide, hydrogen bromide etc.
3. Gases : Hydrogen sulphide, carbon monoxide etc.

Reducing agents generally respond to the following tests :
1. They give out brown fumes of nitrogen dioxide when Warmed with nitric acid.
2. They change black copper (II) oxide on heating to a red copper metal.
3. They decolourise the pink colour of dilute potassium permanganate solution.
4. They change the colour of acidified potassium dichromate solution from orange to green.
5. They change the light yellow colour of iron (III) salts in solution to a light green colour due to the formation of iron (II) salts.

Question 6.
(a) What is the effect of the following pollutants on living beings (one in each case) ?
(i) Fluorides
(ii) Smoke particles
(iii) Lead
(iv) Mercury compounds
(v) Smog
(vi) Nitrogen oxide
Answer:
(i) Fluorides cause destruction of vegetation and affect teeth and bones.
(ii) Smoke particles cause asthma and other lung diseases.
(iii) Lead impairs the body’s metabolic activities.
(iv) They cause diseases like Minamata commonly found in fishermen.
(v) Smog reduces visibility and induces respiratory troubles.
(vi) Nitrogen dioxide causes death of many animals.

(b) Give reason :
(i) Why the temperature of boiling water does not rise even when heat is continuously supplied to it ?
(ii) Why does the salt content in cooked vegetable remain the same, irrespective of whether the cooked food is hot or cold ?
Answer:
(i) The particles of water attract one another with inter particle forces of attraction, and these forces hold the particles together in the liquid state. The heat which we supply to water during boiling is used to overcome these forces of attraction between the particles so that they become totally free and change into a gas. This latent heat does not increase the kinetic energy of water particles, and hence, temperature does not rise during the boiling of water.
(ii) The salt mainly used for cooking purpose is common salt (NaCl) and its solubility does not change with temperature.

ICSE Class 9 Chemistry Sample Question Paper 8 with Answers

(c) Complete the following table which refers to the action of heat on three substances named in the first column.

Substances                               Colour before heating Colour of the residue Name of the gas Name of the residue
(i) Cupric carbonate
(ii) Lead nitrate
(iii) Ammonium dichromate Orange Nitrogen

Answer:

Substances Colour before heating Colour of the residue Name of the gas Name of the residue
(i) Cupric carbonate Green Black Carbon

dioxide

Copper oxide
(ii) Lead nitrate White Reddish yellow Light yellow Nitrogen dioxide and oxygen Lead oxide
(iii) Ammonium dichromate Orange Nitrogen Nitrogen and water vapour Chromium

oxide

Question 7.
(a) What are the main postulates of the kinetic theory of gases ? Explain in brief.
Answer:
Kinetic theory of matter : Any substance whether solid, liquid or gas is made of tiny particles (atoms, molecules or ions) which are in constant motion. This is called the kinetic theory of matter.

Postulates of the kinetic theory of gases are :
1. Composition of matter : Matter is composed of small particles atoms, molecules and ions.

2. Inter-particle space : Particles have spaces between them. These spaces are referred to as inter particle or intermolecular spaces.

3. Inter-particle attraction : Particles attract each other with a force. This force of attraction between the particles of a given substance is called inter-particle attraction or intermolecular force. The inter-particle attraction decreases with increasing distance and vice-versa.

4. Collision of particles : Particles collide with each other and with the walls of the container in both gaseous and liquid states. The total energy of the colliding particles remains the same.

5. Motion of particles : Particles are always in a state of motion. In solids, they vibrate about their fixed mean position. Liquids and gases move randomly. Due to their motion, they possess kinetic energy.

6. Energy possessed by matter : Particles are in a state of constant motion. This random movement of molecules is due to kinetic energy.

ICSE Class 9 Chemistry Sample Question Paper 8 with Answers

(b) Explain the manufacture of hydrogen gas by electrolysis of water.
Answer:
Hydrogen is commercially obtained by the electrolysis of water. Water is a poor conductor of eleectricity. Thus, a less volatile acid such as sulphuric acid is added to water to make it a good conductor of electricity. This is called acidulated water.
ICSE Class 9 Chemistry Sample Question Paper 8 with Answers 9

Water dissociates on passing an electric current through acidulated water.
H2O → H+ + H
H+ being positively charged moves towards the cathode (negatively charged electrode). At cathode,
H+ + e → H
H + H → H2
Thus, hydrogen gas is evolved at the cathode. OH, being negatively charged, moves towards the anode (positively charged electrode). At anode,
OH+ – e → OH
OH + OH → H2O + O
O + O → O2
Oxygen is evolved at the anode.
Hence, water dissociates to give hydrogen and oxygen by passing an electric current through acidulated water.
ICSE Class 9 Chemistry Sample Question Paper 8 with Answers 10

ICSE Class 9 Chemistry Question Papers with Answers

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