Question

Assertion (A): Few drops of dilute hydrochloric acid is added to a solution of iron sulphide, a colourless gas is formed with a rotten egg odour.

Reason (R): The gas formed does not turn moist lead acetate paper silvery black.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Options

• (1)

• (2)

• (3)

• (4)

Answer 1

(3)

Explanation:

When dilute hydrochloric acid is added to iron sulphide (FeS), hydrogen sulphide (H₂S) gas is evolved. It is a colourless gas with a characteristic rotten egg smell. Therefore, the Assertion (A) is true.

Hydrogen sulphide does turn moist lead acetate paper black because black lead sulphide (PbS) is formed. Therefore, the Reason (R) is false.

Hence, A is true and R is false.