MCQ Questions for Class 10 Science: Ch 1 Chemical Reactions and Equations

1. Magnesium ribbon is rubbed before burning because it has a coating of:
(a) basic magnesium oxide
(b) basic magnesium carbonate
(c) basic magnesium sulphide
(d) basic magnesium chloride
► basic magnesium carbonate

2. Which of the following is a thermal decomposition reaction?
(a) 2H2O → 2H2 + O2
(b) 2AgCl → 2Ag + Cl2
(c) H2(g) + Cl2(g) → 2HCl(g)
(d) ZnCO3 → ZnO + CO2
► ZnCO3 → ZnO + CO2

3. When dilute HCl is added to zinc pieces taken in a test tube
(a) No change takes place
(b) the colour of the solution becomes yellow.
(c) A pungent smelling gas gets liberated.
(d) small bubbles of H2 gas appear on the surface of zinc pieces
► (d) small bubbles of H2 gas appear on the surface of zinc pieces.

4. Which of the following reactions will not take place?
(a) Zn + CuSO4 → ZnSO3 + Cu
(b) 2KBr + Cl2 →KCI+ Br2
(c) Zn + MgSO4 → ZnSO4 + Mg
(d) Mg + FeSO4 - MgSO4 + Fe
► (c) Zn + MgSO4 → ZnSO4 + Mg

5. Some crystals of copper sulphate were dissolved in water. The colour of the solution obtained would be:
(a) green
(b) red
(c) blue
(d) brown
► (c) blue

6. Chemically rust is
(a) Hydrated ferrous oxide
(b) hydrated ferric oxide
(c) only ferric oxide
(d) none of these
► (b) hydrated ferric oxide

7. Which of the following involves combination of two elements?
(a) N2(g) + 3H2(g) + 2NH3(g)
(b) Cao(s) + CO2(g) → CaCO3(g)
(c) 2SO2(g) + O2(g) → 2SO3f(g)
(d) NH3(g) + HCl(g) - NH4CI(S)
► (a) N2(g) + 3H2(g) + 2NH3(g)

8. PbS reacts with ozone (O3) and forms pbso4 . As per the balanced equation, molecules of ozone required for every one molecule of PbS is/are
(a) 4
(b) 3
(c) 2
(d) 1
Ans. (a) 4

9. Copper displaces which of the following metals from its salt solution:
(a) ZnSO4
(b) FeSO4
(c) AgNO3
(d) NiSO4
► (c) AgNO3

10. What is observed when a solution of potassium iodide is added to silver nitrate solution?
(a) No reaction takes place
(b) White precipitate of silver iodide is formed
(c) yellow precipitate of Agl is formed
(d) Agl is soluble in water.
► (c) yellow precipitate of Agl is formed

11. Which of the following reactions is not correct:
(a) Zn+ CuSO4 → ZnSO4 + Cu
(b) 2Ag + Cu(NO3)2 → 2AgNO3 + Cu
(c) Fe+CuSO4 → FeSO4 +Cu
(d) Mg + 2HCl → MgCl2 +H2
► (b) 2Ag + Cu(NO3)2 + 2 AgNO3 + Cu

12. When green coloured ferrous sulphate crystals are heated, the colour of the crystal changes because:
(a) it is decomposed to ferric oxide
(b) it loses water of crystallisation
(c) it forms SO2
(d) it forms SO3
► (b) it loses water of crystallisation

13. In an electrolytic cell where electrolysis is carried, anode has:
(a) Positive change
(b) Negative charge
(c) Connected to negative terminal of the battery
(d) None of these is correct
► (a) Positive change

14. Pb + CuCl2 → PbCl2 + Cu
This reaction is an example of:
(a) combination
(b) displacement
(c) decomposition
(d) double displacement
► (b) displacement 

15. A substance which oxidizes itself and reduces other is known as
(a) Oxidising agent
(b) reducing agent
(c) Both (a) and (b)
(d) None of these.
► (b) reducing agent

16. Which of the following gases can be used for storage
(a) Carbon dioxide or Oxygen
(b) Nitrogen or Oxygen
(c) Carbon dioxide or Helium
(d) Helium or Nitrogen
► (d) Helium or Nitrogen

17. Give the ratio in which hydrogen and oxygen are present in water by volume.
(a) 1:2
(b) 1:1
(c) 2:1
(d) 1:8
► (a) 1:2

18. The process of reduction involves
(a) addition of oxygen
(b) addition of hydrogen
(c) removal of oxygen
(d) removal of hydrogen
► (b) addition of hydrogen

19. Oxidation is a process which involves
(a) addition of oxygen
(b) addition of hydrogen
(c) removal of oxygen
(d) removal of hydrogen
► (a) addition of oxygen

19. A substance ‘X’ is used in white-washing and is obtained by heating limestone in the absence of air. Identify ‘X’.
(a) CaOCl2
(b) Ca (OH)2
(c) CaO
(d) CaCO3
► (b) Ca (OH)2

20. Which of the following is an endothermic process?
(a) Dilution of sulphuric acid
(b) Sublimation of dry ice
(c) Condensation of water vapours
(d) Respiration in human beings
► (b) Sublimation of dry ice

21. Select the oxidising agent for the following reaction:
H2S + I2 > 2HI + S
(a) I2
(b) H2S
(C) HI
(d) S
► (a) I2

22. What type of chemical reactions take place when electricity is passed through water?
(a) Displacement
(b) Combination
(c) Decomposition
(d) Double displacement
► (c) Decomposition

23. A substance added to food containing fats and oils is called:
(a) Oxidant
(b) Rancid
(c) Coolant
(d) Antioxidant
► (d) Antioxidant

24. Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is:
(a) 1 : 1
(b) 2:1
(c) 4:1
(d) 1:2
► (b) 2:1

25. Dissolving suger is an example of-
(a) Physical change
(b) Chemical change
(c) Redox Reaction
(d) None of these.
► (a) Physical change

26. The reaction between lead nitrate and potassium iodide present in aqueous solutions is an example of
(a) Decomposition Reaction
(b) Displacement Reaction
(c) Double Displacement Reaction
(d) Neutralisation Reaction
► (c) Double Displacement Reaction

27. Heat is evolved during:
(a) Endothermic Reaction
(b) Displacement Reaction
(c) Combustion Reaction
(d) Combination Reaction
► (c) Combustion Reaction

28. The condition produced by aerial oxidation of fats and oils in foods marked by unpleasant smell and taste is called:
(a) Antioxidation
(b) Reduction
(c) Rancidity
(d) Corrosion
► (c) Rancidity

29. Assertion: Magnesium ribbon keeps on burning in atmosphere of nitrogen.
Reason: Magnesium reacts with nitrogen to form magnesium nitrides and this reaction is combination reaction.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both A and R are false.
► (a) Both A and R are true and R is the correct explanation of A.

30. The reaction between lead nitrate and potassium iodide present in aqueous solutions is an example of
(a) Decomposition Reaction
(b) Displacement Reaction
(c) Double Displacement Reaction
(d) Neutralisation Reaction
► (c) Double Displacement Reaction

31. Assertion: MnO2 + 4HCl → MnCl2 + Cl2 + 2H2O is redox reaction.Reason: MnO2 oxides HCl to Cl2 and gets reduced to MnCl.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both A and R are false.
► (a) Both A and R are true and R is the correct explanation of A.

32. Assertion: A lead nitrate on thermal decomposition gives lead oxide, brown coloured nitrogen dioxide and oxygen gas.
Reason: Lead nitrate reacts with potassium iodide to form yellow ppt of lead iodide and the reaction is double displacement as well as precipitation reaction.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both A and R are false.
► (b) Both A and R are true but R is not the correct explanation of A.

33. Assertion: Zinc reacts with sulphuric acid to form zinc sulphate and hydrogen gas and it is displacement reaction.
Reason: Zinc reacts with oxygen to form zinc oxide.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both A and R are false.
► (b) Both A and R are true but R is not the correct explanation of A.

34. What happens when dilute hydrochloric acid is added to iron filling? Tick the
correct answer
(a) Hydrogen gas and iron chloride are produced.
(b) Chlorine gas and iron hydroxide are produced
(c) No reaction takes place
(d) Iron salt and water are produced
► (a) Hydrogen gas and iron chloride are produced.

35. Which one of the following processes involve chemical reactions?
(a) Storing of oxygen gas under pressure in a gas cylinder
(b) Liquefaction of air
(c) Keeping petrol in a china dish in the open
(d) Heating copper wire in presence of air at high temperature
► (d) Heating copper wire in presence of air at high temperature
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