Read the statements given below and choose the correct option: Assertion (A):…
2024
Read the statements given below and choose the correct option:
Assertion (A): It is recommended that acid should be added to water for diluting the acid and not vice-versa.
Reason (R): Dilution of acid is a highly exothermic reaction.
- A.
Both (A) and (R) are true and (R) is correct explanation of (A).
- B.
Both (A) and (R) are true but (R) is not correct explanation of (A).
- C.
(A) is true but (R) is false.
- D.
Both (A) and (R) are false.
Show answer & explanation
Correct answer: A
CONCEPT: Dissolving a concentrated acid in water is a highly exothermic process -- mixing releases a large quantity of heat, and safe dilution practice requires managing that heat so it does not cause violent boiling or spattering of the corrosive mixture.
APPLICATION: Because dilution of acid releases substantial heat, adding acid in small amounts to a large volume of water lets that large mass of water absorb and disperse the released heat gradually, keeping the temperature rise controlled. If water is instead poured into concentrated acid, the small quantity of water added is heated so intensely by contact with the acid that it can flash to steam, causing sudden, violent spattering of hot, corrosive acid -- a serious safety hazard. This is exactly why acid must always be added to water, never the reverse. So Assertion (A), the safety recommendation, is true, and Reason (R), the exothermic nature of dilution, is not just true but is the direct cause of the safety rule in (A); R correctly explains A.
CROSS-CHECK: This matches the standard NCERT Class 10 Science treatment of Acids, Bases and Salts, and is confirmed by the CTET July 2024 Paper II official answer key.