ICSE Class 9 Chemistry Sample Question Paper 4 with Answers

ICSE Class 9 Chemistry Sample Question Paper 4 with Answers

Section-I
(Attempt all questions from this section)

Question 1.
(a) Fill in the blanks with the correct option given in brackets.
(i) Pollutants such as NO₂, SO₂ and SO₃ dissolved in the moisture of air are the cause of ………….. [water pollution/air pollution]
(ii) Excessive release of carbon dioxide in the atmosphere is the cause of ………….. effect which produces global warming. ………….. [green house/acid rain]
(iii) The ozone layer prevents the harmful radiation of the sun from reaching the earth. ………….. [UV/Infrared]
(iv) Decrease of the concentration of ozone in the stratosphere is the cause of formation of ………….. holes. [black/ozone]
(v) Base turns red litmus ………….. and acid turns blue litmus ………….. [blue/red]
Answer:
(i) Air Pollution
(ii) Green House
(iii) UV
(iv) Ozone
(V) Blue and Red

(b) Choose the correct answer from the options given below :
(i) The gas that prevents haemoglobin from carrying oxygen to different parts of the body is:
(A) Carbondioxide
(B) Carbon monoxide
(C) Hydrogen
(D) Nitrogen
Answer:
(A) Carbondioxide

(ii) Which element is more reactive than zinc ?
(A) Iron
(B) Calcium
(C) Hydrogen
(D) Mercury
Answer:
(B) Calcium

(iii) The isotopes of hydrogen are :
(A) Protium
(B) Deuterium
(C) Tritium
(D) All of the above
Answer:
(D) All of the above

(iv) The gas which has rotten egg smell is :
(A) Hydrogen sulphide
(B) Ammonia
(C) Sulphur dioxide
(D) Hydrogen chloride
Answer:
(A) Hydrogen sulphide

(v) What is the short from that stands for the atom of specific element ?
(A) Valency
(B) Molecular formula
(C) Radical
(D) Symbol
Answer:
(D) Symbol

(c) Name the following :
(i) An oxidising agent which does not contain oxygen.
(ii) A substance which oxidises concentrated HCl to chlorine.
(iii) A substance which will reduce aqueous iron (III) ions to iron (II) ions.
(iv) A liquid which is an oxidising agent as well as a reducing agent.
(v) A solid which is an oxidising agent.
Answer:
(i) Chlorine
(ii) MnO₂
(iii) H₂S
(iv) Hydrogen peroxide
(v) MnO₂

(d) Give reason for each of the following :
(i) Why bonds formed between metals and non-metals are ionic bonds ?
(ii) Dilute nitric acid cannot be used in the preparation of hydrogen.
(iii) Why non-metals form negative ions ?
(iv) Why hydrogen is not collected by the downward displacement of air ?
(v) Why group 17 elements are called most reactive non-metals ?
Answer:
(i) The metals have 1, 2 or 3 electrons in their valence shell. They have a tendency to lose their valence electrons. So, they combine with non-metals which have a tendency to gain electrons and thus form ionic bond.

(ii) Nitric Acid is a very strong oxidising agent. It oxidizes the dihydrogen gas produced during the reaction with metals to form water. That is why nitric acid cannot be used for preparation of hydrogen gas.

(iii) Non-metals form negative ions because non-metals have 5, 6 or 7 electrons in their valence shell and thus have a tendency to gain electron to form negative ions.

(iv) The hydrogen gas is highly combustible and gets oxidized when comes in contact of oxygen. This method is dangerous as the air and hydrogen mixture is explosive and therefore hydrogen is not collected by the downward displacement of air.

(v) Group 17 elements are called most reactive non-metals because they have 7 electrons in their outermost shell and need only 1 electron to become stable.

(e) What do you observe when :
(i) Ammonia reacts with hydrogen chloride gas.
(ii) Lead nitrate crystals are heated strongly.
(iii) The temperature of sodium nitrate and potassium nitrate is increased.
(iv) When barium chloride solution is mixed with sodium sulphate solution.
(v) Dilute hydrochloric acid is added to copper carbonate.
Answer:
(i) Change of state takes place and ammonia gas changes to solid ammonium chloride.
(ii) On heating lead nitrate decomposes to form lead (II) oxide, nitrogen dioxide and oxygen.
(iii) They show considerable increase in their solubilities with rise in temperature.
(iv) A white insolube precipitate of Barium sulphate is obtained.
(v) A brisk effervescence with the release of colourless, odourless, acidic gas that extinguishes glowing splint i.e., carbon dioxide gas is evolved.

(f) (i) State Charle’s law.
(ii) What is the significance of Boyle’s law ?
(iii) What is standard temperature and pressure ?
Answer:
(i) Charle’s law may be stated as volume of a given mass is directly proportional to its absolute temperature, if the pressure remains constant.
\(\frac{\mathrm{V}_{1}}{\mathrm{~T}_{1}}=\frac{\mathrm{V}_{2}}{\mathrm{~T}_{2}}=\mathrm{K}\) at constant Pressure.
Where V₁ is volume occupied by gas 1 at temperature T₁ and V₂ is volume occupied by gas 2 at temperature T₂.

(ii) 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 cylinders with them.

(iii) The standard temperature (T) of a gas is defined as the degree of hotness of that gas. The standard pressure (P) of a gas is the force that the gas exerts per unit area on the walls of its container.

(g) Balance the chemical equations given below :
1. Cl₂ + KBr → 2KCl + Br
2. KClO₃ → 2KCl + O₂
Answer:
1. Cl₂ + 2KBr → 2KCl + 2Br
2. 2KClO₃ → 2KCl + 3O₂

(ii) Identify the substance which matches the description given below :
1. It catches fire and bums with a lilac-coloured flame and produces hydrogen when reacted with water.
2. It acts as a dehydrating agent and removes water molecule from blue vitriol
3. A compound which produces carbon dioxide on heating.
Answer:
1. Potassium when reacts with water bums with a lilac-coloured flame.
2K + 2H₂O → 2KOH + H₂

2. Cone. H₂SO₄ removes water molecules from blue vitriol and acts as a dehydrating agent.

3. Calcium carbonate.

(h) Match Column A with Column B.

Column A	Column B
(i) Red colored compound changes to brown and then yellow	(A) Has 3 isotopes
(ii) Acid turns	(B) Blue litmus red
(iii) Hydrogen	(C) CCl3. NO2
(iv) Tear gas	(D) Copper Sulphate
(v) Caustic soda	(E) NaOH

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

Section – II
(Attempt any four questions from this section)

Question 2.
(a) (i) What are alkaline earth metals ?
(ii) What are halogens ?
(b) What are catalysts and give its types ? Give one example of each ?
(c) Give three conditions for the formation of covalent bond ?
Answer:
(a) (i) The elements of group 13 such as Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba) and Radium (Ra) are alkaline earth metals, because k their oxides occur in the earth’s most and their hydroxides are weak alkalies. All the elements of this group have two valence electrons in their outermost orbit and show ‘ the valency 2.

(ii) Group 17 elements are known as halogens. The name halogens is derived from the Greek word halo which means sea and saltogens which means salt producing. These elements have 7 electrons in their outermost shell. They are all poisonous and have a similar strong pungent and unpleasant odour. They all have valency 1.

(b) Catalyst are those substances which increases or decreases the rate of a reaction without undergoing any change in themselves.

There are two types of catalyst:
1. Positive catalyst : When a catalyst accelerates a reaction, it is known as a positive 1 catalyst. Example : The rate of decomposition of hydrogen peroxide gets increased in the presence of manganese dioxide.
\(2 \mathrm{H}_{2} \mathrm{O}_{2} \stackrel{\mathrm{MnO}_{2}}{\longrightarrow} \mathrm{H}_{2} \mathrm{O}+\mathrm{O}_{2}\)

2. Negative catalyst: A catalyst employed to retard a reaction is known as a negative catalyst.
Example : Phosphoric acid retards the rate of decomposition of hydrogen peroxide.

(c) 1. Combining atom should be short by 1, 2 or 3 electrons in valence shell.
2. Electronegativity difference should be very small or zero between the two atoms.
3. Two atoms should approach one another accompanied by decrease of energy.

Question 3.
(a) (i) Why hydrogen gas is called a strong reducing agent ?
(ii) What is hydrogenation ?
(iii) Write two uses of hydrogen.
Answer:
(i) Hydrogen reduces the oxides of the less active metals i.e., it removes oxygen from strongly metal oxides when passed over them and itself gets oxidized to water.

(ii) In the presence of a catalyst like nickel, hydrogen directly combines with organic compounds that have double or triple bonds between two carbon atoms. This process is known as hydrogenation.

(iii) Uses of hydrogen :
1. Hydrogen is used as a fuel because of its high heat of combustion, hydrogen is used as a fuel in the form of coal gas, water gas and liquid hydrogen.
2. Hydrogen is used in Haber’s process for manufacture of ammonia, hydrogen chloride and methyl alcohol.

(b) (i) What is meant by group and period in a periodic table ?
(ii) What were the reasons to discard the law of octaves ?
(iii) Name two elements each one of which has two electrons in its outermost shell.
Answer:
(i) Vertical columns in the periodic table are called groups and the horizontal rows are called periods.
(ii) The law of octaves was discarded because of the following reasons :
1. The law of octaves was not applicable to the elements of higher atomic masses.
2. With the discovery of noble gases, it was found that it is the ninth element (not eight) that should have properties similar to first one.
(iii) 1. Magnesium (2,8,2)
2. Calcium (2, 8, 8, 2)

(c) Observe the following table showing the arrangement of elements and answer the questions given below the table :

1 2	13	14	15	16	17	18
Lithium		Carbon		Oxygen	L	Neon
X		5		G	Q
Y					R
Z					T

(i) Which is the most reactive metal ?
(ii) Which is the most reactive non-metal ?
(iii) Name the family of L, Q, R, T.
(iv) Name one element from group 15.
Answer:
(i) Z is the most reactive metal.
(ii) L is the most reactive non-metal.
(iii) Halogens.
(iv) Phosphorus is an element of group 15.

Question 4.
(a) At constant temperature, a gas occupies a volume of 2000 cm³ at a pressure of 740 mm of mercury. At what pressure will its volume be 500 cm³ ?
Answer:
Initial volume of the gas, V_x = 2000 cm³
Initial pressure of the gas, P_T = 740 mm Hg
Final volume of the gas, V₂ = 500 cm³
Final pressure of the gas P₂ = ?

(b) A given amount of gas A is confined in a chamber of constant volume. When the chamber is immersed in a bath of melting ice, the pressure of the gas is 100 cm Hg.
(i) What is the temperature when the pressure is 10 cm Hg ?
(ii) What will be the pressure when the chamber is brought to 100°C ?
Answer:
V₁ = V₂ = V
P_x = 100 cm Hg,
T₁ = 273 K,
P₂ = 10 cm Hg,
T₂ =?
\(\frac{P_{1} V_{1}}{T_{1}}=\frac{P_{2} V_{2}}{T_{2}}\)

(c) Gas A’ is a colourless gas which is produced by the reaction of active metals with dilute HCl. Gas ‘B’ is produced by the action of heat on potassium chlorate. Gas ‘A’ undergoes reaction with gas ‘B’ and forms a colourless liquid ‘C’.
(i) Identify A, B and C.
(ii) Give the balanced chemical equation for the formation of liquid ‘C’ from A’ and ‘B’.
(iii) Give two tests to identify liquid ’C’.
Answer:
(i) A – Hydrogen, B – Oxygen, C – Water

(ii) 2H₂ + O₂ 2H₂O

(iii) Liquid ‘C can be tested by the following two ways :
It turns white-coloured anhydrous copper sulphate blue.
It turns blue-coloured anhydrous cobalt chloride pink.

(iv) (a) SO₂ + H₂O → H₂SO₃ Sulphurous acid
(b Na₂O + H₂O → 2NaOH Sodium hydroxide
(c) NH₃ + H₂O → NH₄OH Ammonium hydroxide
(d) CO₂ + H₂O → H₂CO₃ Carbonic acid

(iv) Give the balanced chemical equation for the reaction of ‘C’ with :
(a) Sulphur dioxide
(b) Sodium oxide
(c) Ammonia
(d) Carbon dioxide

Question 5.
(a) (i) Name the isotopes of hydrogen which have mass number 2 and 3 respectively.
(ii) Why do the isotopes of an element have different physical properties ?
(iii) Which isotope of hydrogen has same number of each electron, proton and neutron ?
Answer:
(i) Two isotopes of hydrogen with mass number 2 and 3 are deuterium and tritium respectively.

(ii) The physical properties of the isotopes of an element are different due to the difference in the number of neutrons in their nuclei. The densities, melting points and boiling points etc., are slightly different.

(iii) Deuterium has equal number of electron, proton and neutron in it because it has atomic number one, which is equal to number of electrons and number of protons also.

(b) State the type of covalent bonding in the following molecules :
(i) Chlorine
(ii) Nitrogen
(iii) Oxygen
(iv) Hydrogen
Answer:
(i) Single covalent bond is present in chlorine.
(ii) Triple covalent bond is present in nitrogen.
(iii) Double covalent bond is present in oxygen.
(iv) Single covalent bond is present in hydrogen.

(c) Write the function of ozone layer.
Answer:
Function of Ozone layer :
1. The ozone layer acts as a blanket in the atmosphere above 16 km and prevents the harmful UV rays coming from the sun.
2. It protects life on earth from harmful effects of UV rays which cause skin cancer, destroys many organisms necessay for life in general.
3. The ozone absorbs UV rays of longer wavelength forming oxygen molecule and oxygen atom.

Question 6.
(a) (i) How do fish and aquatic animals survive when a pond is covered with thick ice ?
(ii) Name two elements whose properties were correctly predicted by Mendeleev. Mention their present-day name.
(b) Classify solution on the basis of solubility.
(c) Explain endothermic and exothermic reactions with the help of an example.
Answer:
(a) (i) Water has an unusual physical property. When cooled, it first contracts in volume, as do other liquids, but at 4°C (maximum density), it starts expanding and continues to do so till the temperature reaches 0°C , the point at which it freezes into ice. The property of anomalous expansion of water enables marine life to exist in the colder regions of the world, because even when the water freezes on the surface, it is still liquid below the ice layer.

(ii) Two elements whose properties were correctly predicted by Mendeleev are :
1. Eka-aluminium-Gallium
2. Eka-silicon-Germanium

(b) Solutions can be classified on the basis of their solubility, i.e. depending on the amount of solute which dissolves in a given solvent.

1. Unsaturated solution : If more solute can be dissolved in a solvent at a particular temperature, then the solution is called an unsaturated solution.
2. Saturated solution : If no more solute can be dissolved in a solvent at a particular temperature, then the solution is called a saturated solution.
3. Supersaturated solution : If the solution contains more of the solute, then the saturated solution at a particular temperature is called a ‘supersaturated solution.

(c) Reactions in which heat is given out along with the products are called exothermic reac­tions.
Example : Burning of methane gas releases a large amount of energy. Hence, it is an exothermic reaction.
CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g)
Reactions which absorb energy or require energy in order to proceed are called endothermic reactions.
Example : When ammonium chloride is dissolved in water in a test tube, the test tube becomes cold. Thus, the reaction is an example of an endothermic reaction.

Question 7.
(a) Describe Bohr’s atomic model of an atom.
(b) The table given below shows the mass number and atomic number of five elements A, B, C, D and E.

Element	Mass number	Atomic number
A	35	17
B	23	11
C	12	6
D	16	8
E	40	18

(i) To which group and period does element A belong ?
(ii) Choose from A, B, C, D and E, metal, non-metal and inert gas.
(c) State Newland’s law of octaves.
Answer:
(a) In 1913, Niels Bohr, a Danish physicist, explained the causes of the stability of the atom in a different manner.

Niels Bohr revised Rutherford’s atomic model and put forth the following suggestions :
1. Electrons possess a specific amount of energy which allows them to revolve around the nucleus.
2. An atom contains discrete orbits which correspond to a specific amount of energy.
3. Hence, these orbits are also known as energy levels.
4. The energy levels of an atom are represented as K, L, M, N and so on or the numbers n = 1, 2, 3, 4 and so on.

5. The electrons are confined to these energy levels. While revolving in these discrete orbits, electrons do not radiate energy. Hence, these orbits are also known as ‘stationary orbits’ or ’stationary shells’. Smaller the size of the orbit, smaller is its energy.
6. As we move away from the nucleus, the energy of the orbit increases progressively.
7. The transfer of an electron from one orbit to another is always accompanied with absorp¬tion or emission of energy.
8. When an electron jumps from a lower energy level to a higher energy level, it absorbs energy.
9. When an electron returns from a higher energy level to a lower energy level, it emits energy.

(b) (i) Group = 17
Period 3 (ii) Metal = B
Non-metal = A, D, C Inert gas = E

(c) “If elements be arranged in ascending order of their atomic masses, the properties of eighth element was repetition of properties of first element.” The repetition resembles repetition of eighth note in an octave of music so it is known as law of octaves.

ICSE Class 9 Chemistry Question Papers with Answers