ANS: D
When we add zinc granulated to HCl then the bluish silvery grey colour vanishes and converts in to colourless.
Zn+2HCl - - ->ZnCl2+H2.
Here H2 is evolved where it is an colourless and odourless which is evolved with bubbles in the solution.
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Observations:
(a) The surface of the metal turns shiny.
(b) The reaction mixture turns milky.
(c) Odor of chlorine is observed.
(d) A colorless and odorless gas evolves with bubbles.

Explanation:
When dilute hydrochloric acid is added to granulated zinc placed in a test tube, a chemical reaction takes place. The reaction can be explained as follows:

1. Formation of Zinc Chloride:
Zinc (Zn) reacts with hydrochloric acid (HCl) to form zinc chloride (ZnCl2). This is an example of a displacement reaction, where zinc displaces hydrogen from hydrochloric acid. The reaction can be represented as follows:
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)

2. Shiny Surface:
As the reaction proceeds, the surface of the zinc metal turns shiny. This is because the zinc chloride formed during the reaction forms a protective layer on the surface of the zinc, preventing it from further reacting with the acid. This layer is often referred to as a passivation layer.

3. Milky Mixture:
The reaction mixture turns milky due to the formation of hydrogen gas bubbles. These gas bubbles get trapped in the liquid, giving it a milky appearance.

4. Odor of Chlorine:
The odor of chlorine is observed due to the evolution of chlorine gas (Cl2) during the reaction. Chlorine gas is produced as a byproduct when hydrochloric acid reacts with zinc. However, it is important to note that the odor of chlorine might not be very strong in this reaction, as it is diluted by other gases like hydrogen.

5. Evolution of Gas:
A colorless and odorless gas, hydrogen gas (H2), evolves during the reaction. This gas is formed as a result of the displacement of hydrogen from hydrochloric acid by the more reactive zinc. The evolution of gas can be observed as bubbles rising to the surface of the reaction mixture.

Overall, the addition of dilute hydrochloric acid to granulated zinc results in the formation of zinc chloride, the evolution of hydrogen gas, and the release of chlorine gas, leading to the observed changes in appearance and odor.