Complete the following word equations:

(a) Sodium hydroxide + zinc ⟶ hydrogen + ……………

(b) Calcium + water ⟶ calcium hydroxide + ……………

Hydrogen is evolved by the action of cold dil. HNO₃ on

1. Fe
2. Cu
3. Mg
4. Zn

The composition of the nucleus of deuterium is:

1. 1e^– and 1P
2. 1P and 1n
3. 1n and 1e
4. 2P and 1e^–

Elements which show unique nature in the preparation of hydrogen are

1. Na, K, Li
2. Mg, Ca, Ba
3. Al, Zn, Pb
4. Fe, Cu, Ag