Question

Rahul took some zinc granules in a test tube and added dilute HCI to it. He observed that the colour of the zinc granules changed to

• A. Yellow
• B. Brown
• C. Black
• D. White

Answer 1

The correct option is D

White

Displacement reactions

In a displacement reaction, a less reactive metal is displaced from its salt solution by a more reactive metal. When an element displaced another element from its compound, it is called single displacement reactions. The products of a displacement reaction can be predicted from the reactivity series of metals.

Reaction of Zinc with Hydrochloric acid

Zinc (Zn) is more reactive than hydrogen. Therefore, when Zinc is added to a test tube containing Hydrochloric acid (HCl), it replaces Hydrogen (H) from the solution forming Zinc chloride (ZnCl₂). Hydrogen gas (H₂) is evolved during the reaction.

The balanced equation for the reaction is:

$Zn\left(s\right)+2HCl\left(aq\right)\to ZnC{l}_2\left(aq\right)+H_2\left(g\right)$

(Zinc) (Hydrochloric (Zinc (Hydrogen)

acid) chloride)

Zinc granules have a bluish-silver colour. It is converted to Zinc chloride which is white in colour.

Therefore, the correct option is (D) white.