20 multiple-choice (MCQ / objective) questions from this chapter, in every exam-style shape used in the paper. Every question comes with an explanation along with the answer, so you remember why the option is correct, not just which one it is.
1 Direct Questions
Direct Questions
- 1 markWhat are the substances written on the left side of the arrow in a chemical equation called?
(A) Products(B) Reactants(C) Catalysts(D) Solvents - 1 mark is called what, since the atoms are not equal on both sides?
(A) Balanced equation(B) Skeletal chemical equation(C) Ionic equation(D) Thermochemical equation - 1 markWhich law is the basis for balancing a chemical equation?
(A) Avogadro’s law(B) Law of conservation of mass(C) Boyle’s law(D) Periodic law - 1 markIn , when water is present as steam, which symbol shows this?
(A) (s)(B) (l)(C) (g)(D) (aq) - 1 markOxidation means
(A) loss of oxygen(B) gain of hydrogen(C) gain of oxygen or loss of hydrogen(D) only the loss of an electron - 1 markIn , what happened to the CuO?
(A) Oxidation(B) Reduction(C) Evaporation(D) Sublimation - 1 markWhat happens in an exothermic reaction?
(A) Heat is absorbed(B) Heat is released(C) No energy change occurs(D) Only light is released - 1 markAn example of an endothermic reaction is
(A) Respiration(B) Burning of natural gas(C) Thermal decomposition of (D) Burning of coal - 1 markIn , which form of energy decomposes the AgCl?
(A) Heat(B) Electricity(C) Light(D) Sound - 1 markIn the electrolysis of water (Activity 1.7), the two carbon electrodes collect different volumes of gas. At which one does hydrogen collect, in double the volume of the gas at the other electrode?
(A) the electrode joined to the battery’s negative terminal(B) the electrode joined to the battery’s positive terminal(C) equal at both(D) at neither - 1 markWhich gas is flushed into packets of oily/fatty food to prevent rancidity?
(A) Oxygen(B) Carbon dioxide(C) Nitrogen(D) Hydrogen - 1 markWhat can never be changed while balancing an equation by adding coefficients?
(A) the number of coefficients(B) the chemical formula of a compound(C) the direction of the arrow(D) the state symbols
2 Assertion-Reason
Assertion-Reason
- 1 markAssertion (A): Rusting of iron is a corrosion reaction.
Reason (R): In corrosion, a metal is attacked by substances around it such as moisture, acids, etc.
(A) A true, R true, R explains A(B) A true, R true, R does not explain A(C) A true, R false(D) A false, R true - 1 markAssertion (A): is a double displacement reaction.
Reason (R): In this reaction, zinc displaces copper from its compound.
(A) A true, R true, R explains A(B) A true, R true, R does not explain A(C) A true, R false(D) A false, R true - 1 markAssertion (A): In an exothermic reaction, energy is released along with the product.
Reason (R): Respiration is an exothermic reaction, in which energy is obtained from glucose and oxygen.
(A) A true, R true, R explains A(B) A true, R true, R does not explain A(C) A true, R false(D) A false, R true - 1 markAssertion (A): Thermal decomposition of is an exothermic reaction.
Reason (R): In this reaction, heat must be supplied from outside to break down .
(A) A true, R true, R explains A(B) A true, R true, R does not explain A(C) A true, R false(D) A false, R true
3 Match the Following
Match the Following
- 1 markMatch Column A with Column B:
A: 1. Combination 2. Decomposition 3. Displacement 4. Double displacement
B: (i) Fe+CuSO4→FeSO4+Cu (ii) CaO+H2O→Ca(OH)2 (iii) Na2SO4+BaCl2→BaSO4+2NaCl (iv) CaCO3→CaO+CO2
(A) 1-i, 2-ii, 3-iii, 4-iv(B) 1-ii, 2-iv, 3-i, 4-iii(C) 1-iii, 2-i, 3-iv, 4-ii(D) 1-iv, 2-iii, 3-ii, 4-i - 1 markMatch Column A with Column B:
A: 1. (s) 2. (l) 3. (g) 4. (aq)
B: (i) gas (ii) dissolved in water (iii) solid (iv) liquid
(A) 1-i, 2-ii, 3-iii, 4-iv(B) 1-ii, 2-i, 3-iv, 4-iii(C) 1-iii, 2-iv, 3-i, 4-ii(D) 1-iv, 2-iii, 3-ii, 4-i
4 Passage-Based Questions
Passage-Based Questions
Passage
A student observed in the lab that iron nails dipped in a blue copper sulphate solution turned brownish after a while, and the blue colour of the solution faded. The teacher explained that this is an example of a special kind of reaction, in which one element displaces another element from its compound.
- 1 markWhat type of reaction is described in the passage?
(A) Combination(B) Decomposition(C) Displacement(D) Double displacement - 1 markWhy did the colour of the solution fade in the passage?
(A) The concentration of copper sulphate fell as copper separated out as metal(B) The water evaporated(C) The solution cooled down(D) Because of light
Answer Key and Explanations
Direct Questions
- (B) Substances on the left (LHS) are called reactants; those on the right (RHS) are the products.
- (B) When the number of atoms is unequal on the two sides of an equation, it is called a skeletal (unbalanced) chemical equation.
- (B) By the law of conservation of mass, mass can neither be created nor destroyed, so atoms must be equal on both sides.
- (C) The gaseous state is shown by (g); steam is the gaseous form of water.
- (C) Oxidation = gain of oxygen or loss of hydrogen, exactly as defined in the chapter.
- (B) CuO lost oxygen, so it was reduced.
- (B) In an exothermic reaction, heat is released along with the product forming: respiration is an example.
- (C) Heat must be absorbed to break down CaCO3, so this is endothermic; the other three are all exothermic.
- (C) This is photolytic decomposition: energy comes from sunlight, which is why the reaction is used in black-and-white photography.
- (A) A water molecule () has twice as many hydrogen atoms as oxygen atoms, so twice the volume of H2 collects at the electrode joined to the battery’s negative terminal (the cathode) compared to the O2 at the positive electrode (the anode). Activity 1.7 itself only calls these ‘carbon electrodes’.
- (C) Nitrogen is an inert gas; flushing it in pushes out the oxygen present, slowing down oxidation (rancidity).
- (B) Only coefficients are changed to balance an equation; a compound’s formula is never changed.
Assertion-Reason
- (A) A is true: rusting is an example of corrosion. R is true and is also the correct reason for A.
- (D) A is false: this is a displacement reaction, not double displacement (only one element changed places). R is true and correctly explains why A is false.
- (B) Both A and R are true, but R only gives an example of an exothermic reaction (respiration); it does not explain why energy is released along with the products. So the answer is (B).
- (D) A is false: this is an endothermic reaction (energy is absorbed, not released). R is true and explains exactly why A is wrong.
Match the Following
- (B) Combination = CaO+H2O (ii); decomposition = thermal decomposition of CaCO3 (iv); displacement = Fe+CuSO4 (i); double displacement = Na2SO4+BaCl2 (iii): this is option (B).
- (C) (s)=solid(iii), (l)=liquid(iv), (g)=gas(i), (aq)=dissolved in water(ii): this order is option (C).
Passage-Based Questions
- (C) Iron removed copper from its sulphate compound, so this is a displacement reaction.
- (A) As copper was displaced and deposited as metal, the amount of copper sulphate remaining in the solution kept decreasing, so the blue colour faded.
More for this chapter