Which metal gives hydrogen upon reaction with all of the following - Acid, alkali, water?

1. Iron
2. Zinc
3. Magnesium
4. Lead

A gas which can act as an oxidizing as well as reducing agent:

1. CO
2. NO₂
3. SO₂
4. H₂S

The substance which leaves a black residue on heating is :

1. Zinc carbonate
2. Copper nitrate
3. Lead carbonate
4. Ammonium dichromate.

Name the gas evolved in each of the following cases:

(i) Copper carbonate is heated strongly

(ii) Lead nitrate is heated

(iii) Nitrogen combines with hydrogen

(iv) Copper sulphate is heated strongly

(v) Addition of sodium to cold water