Class X Science (086) – Chemistry Practice Assignment

MCQ Question Bank

Chapter 1 – Chemical Reactions and Equations

1. Identify ‘x’, ‘y’ and ‘z’ in the following reaction :

(a) x = gas; y = reaction condition; z = gas

(b) x = solid; y = liquid; z = gas
(c) x = number of moles of KClO3; y = reaction condition; z = number of molecules of
oxygen
(d) x = physical state of KClO3 and KCl;
y = reaction condition, z = physical state of O2.

2. 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.

3. (a) State the law that is followed by balancing a chemical equation.

(b) Balance the following chemical equation: Na + H2O → NaOH + H2.

4. Explain the significance of photosynthesis. Write the balanced chemical equation

involved in the process.

5. Write balanced chemical equations for the following chemical reactions:

(a) Hydrogen + Chlorine → Hydrogen chloride
(b) Lead + Copper chloride → Lead chloride + Copper
(c) Zinc oxide + Carbon → Zinc + Carbon monoxide

6. Calcium oxide reacts vigorously with water to produce slaked lime.

CaO(s) + H2O(l) → Ca(OH)2(aq)
This reaction can be classified as
(A) Combination reaction​ ​ ​ ​ (B) Exothermic reaction
(C) Endothermic reaction​ ​ ​ ​ (D) Oxidation reaction
Which of the following is a correct option?
(a) (A) and (C)​ (b) (C) and (D)​ (c) (A), (C) and (D)​ ​ (d) (A) and (B)

7. When hydrogen sulphide gas is passed through a blue solution of copper sulphate, a
black precipitate of copper sulphide is obtained and the sulphuric acid so formed
remains in the solution. The reaction is an example of a
(a) combination reaction
(b) displacement reaction
(c) decomposition reaction
(d) double displacement reaction.

8. In a double displacement reaction such as the reaction between sodium sulphate

solution and barium chloride solution :
(A) exchange of atoms takes place
(B) exchange of ions takes place
(C) a precipitate is produced
(D) an insoluble salt is produced
The correct option is
(a) (B) and (D)
(b) (A) and (C)
(c) only (B)
(d) (B), (C) and (D)

9. 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

10. Study the following equation of a chemical reaction:

H2 + Cl2 → 2HCl
(i) Identify the type of reaction.
(ii) Write a balanced chemical equation of another example of this type of reaction.

11. State the type of chemical reactions, represented by the following equations :
(a) A + BC → AC + B
(b) A + B → C
(c) PQ + RS → PS + RQ
(d) A2O3 + 2B → B2O3 + 2A
12. 1 g of copper powder was taken in a China dish and heated. What change takes
place on heating? When hydrogen gas is passed over this heated substance, a visible
change is seen in it. Give the chemical equations of reactions, the name and the colour
of the products formed in each case.

13. A compound ‘A’ is used in the manufacture of cement. When dissolved in water, it
evolves a large amount of heat and forms compound ‘B’.
(i) Identify A and B.
(ii) Write chemical equation for the reaction of A with water.
(iii) List two types of reaction in which this reaction may be classified.

14. Mention with reason the colour changes observe when:

(i) silver chloride is exposed to sunlight.
(ii) copper powder is strongly heated in the presence of oxygen.
(iii) a piece of zinc is dropped in copper sulphate solution.

15. Lead nitrate solution is added to a test tube containing potassium iodide solution.
(a) Write the name and colour of the compound precipitated.
(b) Write the balanced chemical equation for the reaction involved.
(c) Name the type of this reaction justifying your answer.

16. 2 g of silver chloride is taken in a China dish and the China dish is placed in
sunlight for sometime. What will be your observation in this case? Write the chemical
reaction involved in the form of a balanced chemical equation. Identify the type of
chemical reaction.

17. Identify the type of reactions taking place in each of the following cases and write
the balanced chemical equation for the reactions.
(a) Zinc reacts with silver nitrate to produce zinc nitrate and silver.
(b) Potassium iodide reacts with lead nitrate to produce potassium nitrate and lead
iodide.

18. 2 g of ferrous sulphate crystals are heated in a dry boiling tube.

(a) List any two observations.
(b) Name the type of chemical reaction taking place.
(c) Write balanced chemical equation for the reaction and name the products formed.

19. You might have noted that when copper powder is heated in a China dish, the
reddish brown surface of copper powder becomes coated with a black substance.
(a) Why has this black substance formed?
(b) What is the black substance?
(c) Write the chemical equation of the reaction that takes place.
(d) How can the black coating on the surface be turned reddish brown?

20. Decomposition reactions require energy either in the form of heat or light or
electricity for breaking down the reactants. Write one equation each for decomposition
reactions where energy is supplied in the form of heat, light and electricity.

21. Take 3 g of barium hydroxide in a test tube, now add about 2 g of ammonium
chloride and mix the contents with the help of a glass rod. Now touch the test tube
from outside.
(i) What do you feel on touching the test tube?
(ii) State the inference about the type of reaction occurred.
(iii) Write the balanced chemical equation of the reaction involved.

22. (a) A solution of potassium chloride when mixed with silver nitrate solution, an
insoluble white substance is formed. Write the chemical reaction involved and also
mention the type of the chemical reaction.
(b) Ferrous sulphate when heated, decomposes with the evolution of a gas having a
characteristic odour of burning sulphur. Write the chemical reaction involved and
identify the type of reaction.

23. Name the type of chemical reaction represented by the following equation:
(i) CaO + H2O → Ca(OH)2
(ii) 3BaCl2 + Al2(SO4)3 → 2AlCl3 + 3BaSO4

24. What is a reduction reaction? Identify the substances that are oxidised and the
substances that are reduced in the following reactions.
(a) Fe2O3 + 2Al → Al2O3 + 2Fe
(b) 2PbO + C → 2Pb + CO2

25. (a) Can a displacement reaction be a redox reaction? Explain with the help of an
example.
(b) Write the type of chemical reaction in the following:
(i) Reaction between an acid and a base
(ii) Rusting of iron.

26. Mention the type of chemical reaction that takes place when:
(i) a magnesium ribbon is burnt in air.
(ii) limestone is heated.
(iii) silver bromide is exposed to sunlight.
(iv) electricity is passed through acidified water.
(v) ammonia and hydrogen chloride are mixed with each other.

27. What happens when food materials containing fats and oils are left for a long
time? List two observable changes and suggest three ways by which this phenomenon
can be prevented.

28. (i) Why is respiration considered as an exothermic reaction?

(ii) Write chemical name and the formula of the brown gas produced during thermal
decomposition of lead nitrate.
(iii) Why do chips manufactures flush bags of chips with gas such as nitrogen?

29. “We need to balance a skeletal chemical equation.” Give reason to justify the
statement.

30. Name the reducing agent in the following reaction:​

3MnO2 + 4Al———— > 3Mn + 2Al2O3
State which is more reactive, Mn or Al and why?

31. Name the type of chemical reaction represented by the following equation:

32. Write the chemical equation of the reaction in which the following changes have
taken place with an example of each:
(i) Change in colour
(ii) Change in temperature
(iii) Formation of precipitate

33. State the type of chemical reactions and chemical equations that take place in the
following:
(i) Magnesium wire is burnt in air.
(ii) Electric current is passed through water.
(iii) Ammonia and hydrogen chloride gases are mixed.

34. 2g of ferrous sulphate crystals are heated in a dry boiling tube.

(i) List any two observations.
(ii) Name the type of chemical reaction taking place.
(iii) ‘Write the chemical equation for the reaction.

35. (a) Define a balanced chemical equation. Why should an equation be balanced?
(b) Write the balanced chemical equation for the following reaction:
(i) Phosphorus burns in presence of chlorine to form phosphorus pentachloride.
(ii) Burning of natural gas.
(iii) The process of respiration.

36. (a) Explain two ways by which food industries prevent rancidity.
(b) Discuss the importance of decomposition reaction in metal industry with three
points.

37. What is observed when a solution of potassium iodide solution is added to a

solution of lead nitrate? Name the type of reaction. Write a balanced chemical
equation to represent the above chemical reaction.

38. Write chemical equation reactions taking place when carried out with the help of
(a) Iron reacts with steam
(b) Magnesium reacts with dil HCl
(c) Copper is heated in air.

39. (a) Write one example for each of decomposition reaction carried out with help of
(i) Electricity (ii) Heat (iii) Light
(b) Which of the following statements is correct and why copper can displace silver
from silver nitrate and silver can displace copper from copper sulphate solution.

40. What is meant by the skeletal chemical equation? What does it represent? Using
the equation for electrolytic decomposition of water, differentiate between a skeletal
chemical equation and a balanced chemical equation.

41. Identify the type of reaction(s) in the following equations.

(i) CH4 + 2O2 CO2 + 2 H2O
(ii) Pb(NO3)2 + 2KI ——–>Pbl2 + 2KNOs
(iii) CaO + H2O ——–> Ca(OH)2
(iv) CuSO4 + Zn ——–> ZnSO4 + Cu

42. What is the colour of ferrous sulphate crystals? How does this colour change after
heating?
43. Why does the colour of copper sulphate solution change when an iron nail is
dipped in it? Write two observations.

44. Translate the following statement into a chemical equation and then balance it.
Barium chloride reacts with aluminium sulphate to give aluminium chloride and a
precipitate of barium sulphate. State the two types in which this reaction can be
classified.

45. Why are decomposition reactions called the opposite of combination reactions?
Write equations for these reactions.

46. A zinc plate was put into a solution of copper sulphate kept in a glass container. It
was found that the blue colour of the solution gets fader and fader with the passage of
time. After a few days, when the zinc plate was taken out of the solution, a number of
holes were observed on it.
(i) State the reason for changes observed on the zinc plate.
(ii) Write the chemical equation for the reaction involved.