Question

2. Zinc granules on treating with an acid X, form the zinc sulphate (ZnSO4) salt
along with the evolution of a gas Y which burns with a pop sound when brought
near to a burning candle. Identify the acid X and gas evolved Y. (1 MARK)
(a)X- Sulphuric acid and Y- Oxygen gas (b) X- Hydrochloric acid and Y- Oxygen
gas
(c) X- Sulphuric acid and Y- Hydrogen gas (d) X- Hydrochloric acid and Y-
Hydrogen gas​

Answer 1

Answer:

c) X- Sulphuric Acid Y- Hydrogen gas

Explanation:

When a metal reacts with an acid, always single displacement reaction occurs.

Metal + Acid ----------> Salt + Hydrogen gas

So, now with this knowledge, we can easily determine the acid. The end product will always have hydrogen in it so, it is already predicted.

The salt given here is ZnSO₄ or zinc sulphate.

The negative radical is a sulphate ion or SO₄²⁻.  

We know, zinc lies above hydrogen in the metal reactivity series and hence, always displaces hydrogen from a hydrogen compound with hydrogen as cation.

Then, here also, zinc displaces Hydrogen from its compound. The presence of negative charge on the radical indicates that hydrogen is the cation in the acid. It is always the cation.

So, the acid with sulphate ion is none other than Sulphuric acid.

Zn + dil. H₂SO₄ ----------> ZnSO₄ + H₂ (g)