The acid which can be used to etch designs on brassware is :

1. HCl
2. HNO₃
3. H₂SO₄
4. H₂CO₃

HNO₃ is kept in reagent bottles because it is :

1. an oxidising agent
2. a reducing agent
3. hygroscopic in nature
4. decompose in the presence of light

On heating zinc nitrate, the products formed are zinc oxide, nitrogen dioxide and oxygen. Zinc oxide is :

P — a black solid

Q — brown when hot, yellow when cold

R — yellow when hot, white when cold

Which of the following is true ?

1. Only P
2. Only Q
3. Only R
4. Both Q and R

Assertion (A): KNO₃ and conc. H₂SO₄ are the reactants for the preparation of nitric acid.

Reason (R): Conc. H₂SO₄ being a non volatile acid is required to prepare volatile acids.

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.