Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other? Name this gas.

Why does the colour of copper sulphate solution change when an iron nail is dipped in it?

Identify the substances that are oxidised and the substances that are reduced in the following reactions.

(i) 4Na (s) + O₂ (g) ⟶ 2Na₂O (s)

(ii) CuO (s) + H₂ (g) ⟶ Cu (s) + H₂O (l)

Which of the statements about the reaction below are incorrect?

2PbO (s) + C (s) ⟶ 2Pb (s) + CO₂ (g)

(a) Lead is getting reduced.

(b) Carbon dioxide is getting oxidised.

(c) Carbon is getting oxidised.

(d) Lead oxide is getting reduced

1. (a) and (b)
2. (a) and (c)
3. (a), (b) and (c)
4. all