Assertion (A): Efflorescence is minimum during humid conditions.
Reason (R): Efflorescence occurs when the vapour pressure of the hydrated crystals exceeds the vapour pressure of the atmospheric humidity.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Both A and R are true and R is the correct explanation of A.
Explanation — In humid conditions, the atmospheric vapour pressure increases. Therefore, the difference between the vapour pressure of the hydrated salt and the atmosphere is less, and water does not easily escape from the crystals. Thus, efflorescence is minimized. Hence the assertion (A) is true.
Efflorescence occurs when vapour pressure in the hydrated crystals is higher than atmospheric vapour pressure. Hence reason (R) is true.
Reason (R) explains why efflorescence occur and how vapour pressure of crystal varies according to atmospheric humidity. Hence, reason (R) is correct explanation for assertion (A).