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Chemical Reaction and Equation


Previous Years' CBSE Board Questions
1.1 Chemical Equations
MCQ
1. Sodium reacts with water to form sodium hydroxide and hydrogen gas. The
balanced equation which represents the above reaction is




2. It is important to balance the chemical equations to satisfy the law of
conservation of mass. Which of the following statements of the law is
incorrect?
(a) The total mass of the elements present in the reactants is equal to the total
mass of the elements present in the products.
(b) The number of atoms of each element remains the same, before and after a
chemical reaction.
(c) The chemical composition of the reactants is the same before and after the
reaction.
(d) Mass can neither be created nor can it be destroyed in a chemical reaction.
(Term 1, 2021-22)
3. In which of the following, the identity of initial substance remains
unchanged?
(a) Curdling of milk
(b) Formation of crystals by process of crystallisation
(c) Fermentation of grapes
(d) Digestion of food (2020)
4. Identify 'x, 'y' and 'z' in the following reaction: 2KCIO32KC+026)
(a) x=gas: y = reaction condition; z = gas

,(b) x=solid; y = liquid; z = gas
(c) x = number of moles of KCIO3: y = reaction condition; z = number of
molecules of oxygen
(d) x = physical state of KCIO, and KCI; y = reaction condition, z=physical
state of O₂ (2020)
5. Assertion (A): Following is a balanced chemical equation for the action of
steam on iron: 3Fe+ 4H2O-Fe3O4+4H2
Reason (R): The law of conservation of mass holds good for a chemical
equation.
(a) Both (A) and (R) are true and reason (R) is the correct explanation of the
assertion (A).
(b) Both (A) and (R) are true, but reason (R) is not the correct explanation of
the assertion (A).
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true. (2020)
VSA (1 mark)
6. What is a balanced chemical equation? (2021 C)
7. Translate the following statement into a balanced chemical equation:
"Barium chloride reacts with aluminium sulphate to give aluminium chloride
and barium sulphate." (2019)
SAI (2 marks)
8. Give the chemical name of the reactants as well as the products of the
following chemical equation: HNO3 + Ca(OH)2 Ca(NO3)2 + H2O (2021 C)
SA II (3 marks)
9. Explain the significance of photosynthesis. Write the balanced chemical
equation involved in the process. (Board Term I, 2017) U
10. Write balanced chemical equations for the following chemical reactions:
(a) Hydrogen+Chlorine→→→ Hydrogen chloride (NCERT Intext)
(b) Lead + Copper chloride →→ Lead chloride +Copper (Board Term 1, 2014)
(c) Zinc oxide + Carbon→ Zinc+Carbon monoxide
1.2 Types of Chemical Reactions
MCQ

, 11. When aqueous solutions of potassium iodide and lead nitrate are mixed,
an insoluble substance separates out. The chemical equation for the reaction
involved is




12. A metal ribbon 'X' burns in oxygen with a dazzling white flame forming a
white ash 'Y. The correct description of X, Y and the type of reaction is
(a) X Ca; Y=CaO;
Type of reaction = Decomposition
(b) X-Mg: Y=MgO;
Type of reaction = Combination
(c) X-Al; Y Al2O3:
Type of reaction = Thermal decomposition
(d) X=Zn; Y=ZnO;
Type of reaction = Endothermic (2023)
13. The balanced chemical equation showing reaction between quick lime and
water is
(a) 2CaO+H₂O→2CaOH+H₂+ Heat
(b) CaO+H2O→Ca(OH)2 + H2 + Heat
(c) CaO+H₂O→→ Ca(OH)2 + Heat
(d) 2CaO+ 3H2O→2Ca(OH)3+0₂+ Heat (2023)
14. Study the following chemical reaction:
2Na(s)+2H2O→2NaOH(aq) + H2(g)
The reducing agent in this reaction is
(a) Na (b) H₂O (c) NaOH (d) H₂ (2023)
15. Assertion (A): In the following reaction
ZnO+C-Zn + CO
ZnO undergoes reduction.
Reason (R): Carbon is a reducing agent that reduces ZnO to Zn.
(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct
explanation of the Assertion (A)
(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the