ICSE Class 9 Chemistry Sample Question Paper 5 with Answers

ICSE Class 9 Chemistry Sample Question Paper 5 with Answers

Section-I
(Attempt all questions from this section)

Question 1.
(a) Fill in the blanks with the correct choice given in brackets.
(i) The reaction between an acid and a base that forms slat and water only is known as ……………… [precipitation / neutralization]
(ii) Carbonates of …………. and potassium do not produce carbon dioxide on heating. [sodium/aluminium]
(iii) The reactions in which the direction of chemical change can be reversed by changing the conditions is known as …………… reaction, [reversible/irreversible]
(iv) A solution in which more of the solute can be dissolved at a given temperature is known as …………….. [unsaturated/saturated solution]
(v) ……………. is the example of hydrated substance. [Table salt/Copper sulphate pentahydrate]
Answer:
(i) Neutralization
(ii) Sodium
(iii) Reversible reaction
(iv) Unsaturated solution
(v) Copper sulphate pentahydrate

(b) Choose the correct answer from the options given below :
(i) The symbolic representation of a molecule is known as :
(A) Molecular formula
(B) Formula
(C) Chemical formula
(D) All of the above
Answer:
(D) All of the above

(ii) Elements having only one atom in their molecular are known as :
(A) Diatomic molecule
(B) Monoatomic molecule
(C) Triatomic molecule
(D) Tetratomic molecule
Answer:
(B) Monoatomic molecule

(iii) Hygroscopic substances are :
(A) Cone. Sulphuric acid
(B) Quicklime
(C) P₂O₅
(D) All of the above
Answer:
(D) All of the above

(iv) P₁V₁ = P₂V₂ is which law ?
(A) Charle’s law
(B) Boyle’s law
(C) Gas law
(D) None of the above
Answer:
(B) Boyle’s law

(v) If pressure is doubled for a fixed mass of a gas, its volume will become
(A) 1/2 times
(B) no change
(C) 4 times
(D) 2 times
Answer:
(D) 2 times

(c) Name the reducing agent in the following reactions :
(i) Fe₂O₃ + 3CO → 2Fe + 3CO₂
(ii) CuO + H₂ → Cu + H₂O
(iii) ZnO + C → Zn + CO
(iv) 3CuO + 2NH₃ → 3Cu + N₂ + 3H₂O
(v) PbO + C → Pb + C
Answer:
(i) Carbon monoxide
(ii) Hydrogen
(iii) Carbon
(iv) Ammonia
(v) Carbon

(d) Give a reason for each of the following :
(i) Metals form positive ions.
(ii) Why should an equation be balanced ?
(iii) Why deliquescence is minimized during dry conditions ?
(iv) Why quick lime acts as a drying agent ?
(v) Noble gases do not combine with other elements to form molecules.
Answer:
(i) In order to attain stable state metals lose their valence electrons and form positive ions.
(ii) An equation must be balanced in order to comply with the “law of conservation of matter” which states that matter is neither created nor destroyed in the course of a chemical reaction. An unbalanced equation would imply that atoms have been created or destroyed.
(iii) Deliquescence occurs when vapour pressure inside the crystals is very low compared to vapour pressure in the atmospheric air. Thus deliquescence is minimized during dry conditions.
(iv) Quicklime being basic in nature is suitable for drying NH₃, a basic gas. Basic gas will not react with base.
(v) Noble gases do not combine with other elements to form molecules because they have 8 electrons in their outermost orbits, except helium which has 2.

(e) Answer the following questions :
(i) Write a chemical reaction which proceeds with the absorption of sound energy.
(ii) Write a chemical reaction depicting change of state.
(iii) Write two uses of neutralization.
(iv) Write the importance of dissolved salts in water.
(v) What is a solution?
Answer:
(i) Acetylene breaks up into carbon and hydrogen by absorbing sound energy.
\(\mathrm{C}_{2} \mathrm{H}_{2} \stackrel{(\text { sound energy })}{\longrightarrow} 2 \mathrm{C}+\mathrm{H}_{2}\)

(ii) Ammonia gas reacts with hydrogen chloride gas to produce solid ammonium chloride.
\(\mathrm{NH}_{3}(\mathrm{~g})+\mathrm{HCl}(\mathrm{g}) \rightleftharpoons \mathrm{NH}_{4} \mathrm{Cl}(\mathrm{s})\)

(iii) 1. Acid that is accidentally spilled into our clothes or body can be neutralized with ammonia solution.
2. If the soil is some what acidic, and thus unfavourable for growing of certain crops, slaked lime is added to neutralize the excess acid.

(iv) 1. They are essential for growth and development of plants.
2. They add taste to water.

(v) A solution is a homogeneous mixture of two or more components whose composition may be gradually changed by changing the relative amounts of the compounds.

(f) (i) Write the cleansing action of soaps and detergents.
(ii) Answer the following questions :

1. Name the shell denoted by A, B, C. Which shell has the least energy.
2. Name X, state the change on it.
3. The above sketch is………………… model of an atom.

(iii) What was was the basis of Mendeleev’s periodic law.
Answer:
(i) When a soap or detergent is dissolved in water, the molecules gather as clusters called micelles. The tails stick inwards and the head outwards.

In cleansing action, the hydrocarbon tail attaches itself to oily dirt. When water is stirred, the oily dirt tends to lift off from the dirty surface and dissociates into fragments. This gives an opportunity to other tails to stick to oil. The solution now contains small globules of oil surrounded by detergent molecules. The negatively charged heads present in water prevent the small globules from coming together and form aggregates. Thus, the oily dirt is removed from the object.

(ii) 1. The shell denoted by A is K, B is L and C is M. The orbit close to the nucleus has the least amount of energy.
2. X is nucleus and it has positive charge.
3. The above sketch is of Bohr’s model of an atom.
Mendeleev’s periodic law was bared on atomic masses.

(g) (i)
1. What is a balanced chemical equation ?
2. Write the partial equation method for balancing a chemical equation.
Answer:
1. It is an equation in which the total number of atoms of each element in the reactants, on the left side of the equation, is the same as the number of atoms in the products formed, on the right side of the equation.

2. Balancing can be done more easily by supposing the complex reaction to take place in steps. Write the equations for these individual steps and then add the equations. This method is known as balancing by partial equation method.

(ii) Balance the following chemical equations :
1. As₂O₃ + SnCl₂ + HCl → SnCl₄ + 2As + H₂O
2. Cu + H₂SO₄ → CuSO₄ + SO₂ + H₂O
3. Mg(s) + H₂SO₄(dil.) MgSO₄(aq) + H(g)
Answer:
1. As₂O_s + 3SnCl₂ + 6HCl → 3SnCl₄ + 2As + 3H₂O
2. Cu + 2H₂SO₄ → CuSO₄ + SO₄ + 2H₂O
3. Mg(s) + H₂SO₄(dil.) → MgSO₄(aq) + 2H(g)

(h) Match Column A with Column B.

Column A	Column B
1. Positive ions are known as 2. Photosynthesis 3. Chemical name of water 4. Negative ions are known as 5. Alloys	(A) Dihydrogen oxide (B) Cations (C) Chlorophyll (D) A solid with another solid (E) Anions

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

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

Question 2.
(a) Define the following terms :
(i) Valency
(ii) Cation
(iii) Symbol
Answer:
(a) (i) Valency is the number of electrons, that atom can lose, gain or share during a chemical reactions.
(ii) Cation is a positively charged ion which is formed when an atom loses one or more electrons.
(iii) A Symbol is the short form which stands for the atom of a specific elements or the abbreviations used for the names of elements.

(b) (i) What is an element ?
(ii) What are the constituents of an atom ?
(iii) Arrange in an increasing order of atomic size (Cl, I, Br).
Answer:
(i) Element is a substance which cannot be split up into two or more simple substances by usual chemical methods of applying heat, light or electric energy; for example, hydrogen, oxygen and chlorine.
(ii) Nucleus (protons, neutrons) with associated electrons; mass number and atomic number are the constituents of an atom.
(iii) Cl < Br < I

(c) What does a balanced chemical equation convey? Explain in detail.
Answer:
A chemical equation gives following information :
1. The actual result of a chemical change.
2. The substances which take part in a chemical reaction, and the substances which are formed as a result of the reaction.
3. The number of atoms of each element participating in the reaction.
4. The number of molecules of different substances taking part in the chemical reaction.
For example :     Zn + H₂SO₄ ZnSO₄ + H₂
5. Here, one molecule of zinc and one molecule of sulphuric acid react to give one molecule of zinc sulphate and one molecule of hydrogen.
6. Composition of respective molecules, for example : One molecule of sulphuric acid contains two atoms of hydrogen, one atom of sulphur and four atoms of oxygen.
7. Relative molecular masses of different substances, for example : molecular mass of following elements and compounds.
(a) Zn = 65,
(b) H₂SO₄ = (2 + 32 + 64) = 98
(c) ZnSO₄ = (65 + 32 + 64) = 161
(d) H₂ = 2
8. It tells about the volume of gaseous reactants and products.
Example :
N₂ + 3H₂  → 2NH₃
1 vol. 3 vol. 2 vol.

Question 3.
(a) Write a short note on occurrence of hydrogen.
(b) Explain why in the laboratory, hydrogen is not prepared by the reaction of lead with dilute sulphuric acid or dilute hydrochloric acid.
(c) Write general trends of the Modem periodic table.
Answer:
(a) Free State : In free state, hydrogen is found in traces in the earth’s crust and atmosphere. Volcanic gases contain 0.025% of it, the earth’s crust 0.98%, the earth’s atmosphere 0.01% and the atmosphere of the sun and the stars contain 1.1% hydrogen.

Combined State :
1. Plant and animal tissues are made up of compounds of hydrogen with carbon, oxygen and nitrogen.
2. Hydrogen is the characteristics constituent of acids, alkalis, hydrogen and proteins. In addition to these, sugar, starch, petroleum products, proteins, carbohydrates and also fats contain hydrogen.

(b) In the laboratory, hydrogen is not prepared by the reaction of lead with dilute sulphuric acid or dilute hydrochloric acid because it forms insoluble lead sulphate and insoluble lead chloride, respectively, which prevents the reaction of metals with acids.

(c) General trends of the Modem periodic table :

Groups :
1. Numbers of shells and valence electrons : Number of shells increases arithmetically and number of valence electrons remains equal to the number of the group to which the element belongs. Also, number of electron shells in a given element to the number of period to which it belongs.

2. Valency : Valency of an element equals the number of electrons present in its valence shell. Valency for all the elements in a group is same.

3. Properties of Elements : Elements in a given group possess similar electronic configuration because the number of electrons in their respective outermost shells is the same, hence they have similar physical and chemical properties.

4. Atomic Size : As one moves down a group, size of atoms of successive elements increases.

5. Metallic character : Metallic character increases as one moves down a group.

Periods :
1. Number of shells : On moving from left to right in a given period, number of shells remains the same.
2. Number of electrons in valence shell : In a given period, number of electrons in valence shell increases from left to right.
3. Valency : Valency of elements, with respect to hydrogen, increases arithmetically from 1 to 4 and
back to 1.
4. Size of Atoms : Size of atoms decreases when moving left to right in a period.
5. Metallic character : On moving from left to right in a period metallic character gradually decreases i.e. changes from metallic to non-metallic.

Question 4.
(a) Which of the lettered elements is :

(i) An inert gas
(ii) A transition element
(iii) An alkali metal
(iv) An alkaline earth metal
(v) A halogen
(vi) Forms a diatomic molecule
Answer:
(i) C,I
(ii) F,G
(iii) D
(iv) A
(v) H
(vi) B and H

(b) How will you incorporate the following information into an equation ?
(i) Temperature and pressure conditions
(ii) Formation of precipitate
(iii) Evolution of a gas
Answer:
(i) The temperature and pressure conditions are written above or below the arrow.
(ii) Formation of a precipitate is depicted by a downward arrow
(iii) Evolution of a gas is depicted by an upward arrow.

(c) Convert the following temperature (in °C) to the Kelvin scale.
(a) – 100°C
(ii) 273°C
(iii) 20°C
(iv) 5°C
(v) 300°C
Answer:
(i) -100°C = – 100 + 273 = 173 K
(ii) 273°C = 273 + 273 = 546 K
(iii) 20°C – 20 + 273 = 293 K
(iv) 5°C = 5 + 273 = 278 K
(v) 300°C = 300 + 273 = 573 K

Question 5.
(a) Explain what you understand from the following diagram :

Answer:
1. When a soild changes into a liquid, it absorbs heat equal to the latent heat of fusion. When a liquid changes into a solid, it loses heat equal to the latent heat of solidification.
2. When a liquid changes into a gas, it absorbs heat equal to the latent heat of vapourization. When a gas condenses into a liquid, it loses heat equal to the latent heat of condensation.

(b) (i) Why does the temperature of boiling water not rise even when heat is continuously supplied to it ?
(ii) Write the process of removal of temporary hardness by boiling water.
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) By boiling carbon dioxide is driven off and the soluble hydrogen carbonates are converted into insoluble carbonates and could be removed by filtration or decantation.
Ca(HCO₃)₂ → CaCO₃ + H_zO + CO₂
Calcium carbonate and magnesium carbonate are precipitated leaving the water soft. This is however, not very practical when large quantities of water are concerned.

(c) Give electron dot diagram of the following :
(i) Magnesium chloride
(ii) Nitrogen
(iii) Methane
(iv) Hydrogen chloride
Answer:

Question 6.
(a) Write the process of removal of hardness by Clark’s process.
(b) Give difference between a deliquescent substance and a hygroscopic substance.
(c) What are photochemical and electrochemical reactions ?
Answer:
(a) Clark’s process : A more practical method is to add a calculated quantity of slaked lime. The following reaction takes place.
Ca(HCO₃)₂ + Ca(OH)₂ → 2CaCO₃ + 2H₂O
Mg(HCO₃)₂ + Ca(OH)₂ → MgCO₃ + CaCO₃ + 2H₂O
Lime is first thoroughly mixed with water in a tank and then fed into another tank con­taining the hard water. Revolving paddles thoroughly mix the two solutions. Most of the calcium carbonate settles down. If there is any solid left over it is removed by a filter. The process goes by the name of Clark’s process.

(b)

Deliquescent substances	Hygroscopic substances
Water-soluble salts absorb moisture from the atmosphere and dissolve in it to form a saturated solution. The substance is called a deliquescent substance and the phenomenon is called deliquescence.	When a substance can absorb moisture from the air without changing its state (solid/liquid), the substance is called hy­groscopic and the phenomenon is known as hygroscopy.
They are solid crystalline in nature.	They may be crystalline solid or liquids.
They absorb moisture from the atmosphere and dissolve in it to form a saturated solution.	They absorb moisture from the atmo­sphere and dissolve in it but do not form a saturated solution.
Examples : Caustic soda (NaOH), caustic Potash (KOH), magnesium chloride (MgCy, zinc chloride (ZnCl2), ferric chloride (FeCl2).	Examples : Copper oxide (CuO), calcium oxide (CaO), copper sulphate (CuSO4), concentrated sulphuric acid (H2SO4).

(c) 1. Photochemical reaction : It is a reaction that occurs with the absorption of light energy.
Examples : Photosynthesis

2. Electrochemical reactions : It is a reaction that occurs with absorption of electrical energy.
Examples: (i) Fused potassium chloride, on passing current through it, breaks into charged particles of potassium and chloride.
\(\mathrm{KCl} \stackrel{\text { Electric current }}{\longrightarrow} \mathrm{K}^{+}+\mathrm{Cl}^{-}\)
(ii) Acidulated water breaks into hydrogen and oxygen.
\(2 \mathrm{H}_{2} \mathrm{O} \stackrel{\text { Electric current }}{\longrightarrow} 2 \mathrm{H}_{2}+\mathrm{O}_{2}\)

Question 7.
(a) Complete the following table :

Answer:
Atomic number of an element = No. of protons = No. of electrons Atomic number of phosphorus = 15 Therefore no. of protons in phosphorus = 15 And no. of electrons = 15

Mass number of an element = No. of protons + No. of neutrons Mass number of phosphorus = No. of protons + No. of neutrons 31-15 = 16 = No. of neutrons

Atomic number of an element = No. of protons = No. of electrons Atomic number of potassium = 19 Therefore No. of protons in potassium = 19 And No. of electrons = 19

Mass number of an element = No. of protons + No. of neutrons Mass number of potassium = 19 + 20 = 39

(b) Write the electronic configuration of the following :
(i) Potassium
(ii) Sulphur
Answer:
(i) Is² 2s² 2p⁶ 3s² 3p⁶ 4s¹
(ii) Is² 2s² 2p⁶ 3s² 3p⁴

(c) State the valency of the element having :
(i) 4 electrons in its valence shell
(ii) Having electronic configuration 2, 2
Answer:
(i) Valency is 4 and the element is silicon.
(ii) Valency is 2 and the element is beryllium.

ICSE Class 9 Chemistry Question Papers with Answers