Chapter 1 Chemical Reactions and Equations Assertation & Reasoning Questions Class 10th Science

Direction: In the following questions, a statement of Assertion (A) is followed by a statement of Reason (R). Mark the correct choice as:
(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
(b) Both Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of
Assertion (A).
(c) Assertion (A) is true but Reason (R) is false.
(d) Assertion (A) is false but Reason (R) is true

Q1. 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.

Answer. (a) Both A and R are true and R is the correct explanation of A.

Q2. 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.

Answer. (a) Both A and R are true and R is the correct explanation of A.

Q3. 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.

Answer. (b) Both A and R are true but R is not the correct explanation of A.

Q4. 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.

Answer. (b) Both A and R are true but R is not the correct explanation of A.

Q6. ASSERTION:  Combustion reactions are also called exothermic oxidation reactions.
REASON:  In these reactions, oxygen is added and heat energy is released.

(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.

Answer. (A) Both assertion and reason are correct and the reason is the CORRECT explanation of the assertion.

Q7. ASSERTION:  Colour of copper sulphate does not change when an iron nail is kept in it.
REASON:   Iron is more reactive than copper and it displaces it.

(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

Answer. (D) Assertion is incorrect. Iron is more reactive displaces Cu and forms FeSO₄ which changes the colour.

Q8. ASSERTION:  White silver chloride turns grey in the presence of sunlight.
REASON:    In the presence of the sunlight, silver chloride decomposes into silver metal and chlorine gas.

(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.

Answer. (A) Both assertion and reason are correct and the reason is the

CORRECT explanation of the assertion.

Q9. ASSERTION: Calcium carbonate on heating breaks into Calcium Oxide and Cabon dioxide gas.
REASON:  Calcium carbonate is a base.

(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.

Answer. (B) If both assertion and reason are CORRECT, but the reason is NOT THE CORRECT explanation of the assertion.
   CaCO₃ breaks due to thermal decomposition and it is an endothermic reaction.

Q10. ASSERTION:  Rusting of iron is a chemical change.
REASON:  The chemical properties of hydrated iron oxide are different from iron and oxygen.

(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.

Answer. (A) Both assertion and reason are correct and the reason is the CORRECT explanation of the assertion.

Q11. ASSERTION: The chemical reaction during which hydrogen is lost is called as reduction reaction.
REASON: Reducing agent removes hydrogen.

(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.

Answer. (E) If both assertion and reason are INCORRECT

Q12. ASSERTION: Nitrogen is flushed in potato chip packets to preserve acidity of potato chips.
REASON:    Nitrogen prevents contact of chips to air and thus prevents oxidation.

(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.

 Answer. (D) If the assertion is INCORRECT, but the reason is CORRECT
   Nitrogen is flushed to avoid potato chips getting rancid.

Q13. Assertion : Corrosion of iron is commonly known as

rusting.

Reason : Corrosion of iron occurs in presence of water

and air.

(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.

Ans : (b) If both Assertion and Reason are correct,

but Reason is not the correct explanation of

Assertion.

Corrosion occurs due to oxidation of iron.

Q14. Assertion : In a reaction.

Zn(s) + CuSO4 (aq) 🡪 ZnSO4 (aq) + Cu(s) 

Zn is a reductant but itself get oxidized.

Reason : In a redox reaction, oxidant is reduced by

accepting electrons and reductant is oxidized by losing

electrons.

(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.

Ans : (a) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.

Q15. Assertion : A reducing agent is a substance which can

either accept electron.

Reason : A substance which helps in oxidation is

known as reducing agent.

(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.

Ans : (d) If Assertion is incorrect but Reason is correct

A reducing agent is a substance which oxidizes itself but reduces others i.e., looses electrons.

Q16. Assertion : The balancing of chemical equations is

based on law of conservation of mass.

Reason : Total mass of reactants is equal to total mass

of products.

(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.

Ans : (a) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.

Q17. Assertion (A) : Carbon dioxide turns lime water milky.

Reason (R) : Carbon dioxide sullies the water.

(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.

Ans : (c) Assertion (A) is true but reason (R) is false. Carbon dioxide reacts with lime water (calcium

hydroxide) to form milky precipitate of calcium carbonate.

Q18. Assertion (A) : A chemical reaction becomes faster at higher temperatures.

Reason (R) : At higher temperatures, molecular motion becomes more rapid.

(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.

Ans : (a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).