Question

The nitrate which on thermal decomposition leaves behind a residue which is yellow when hot and white when cold:

Options

• Lead nitrate

• Ammonium nitrate

• Copper nitrate

• Zinc nitrate

Answer 1

Zinc nitrate

Explanation:

When zinc nitrate [Zn(NO₃)₂] undergoes thermal decomposition, it breaks down to form zinc oxide (ZnO), nitrogen dioxide gas, and oxygen gas. The resulting zinc oxide residue exhibits a characteristic physical property known as thermochromism: it appears yellow when hot due to a reversible loss of oxygen from its crystal lattice, and turns white again when it cools.