When hydrogen is passed over a black solid compound A, the products are 'a colourless liquid' and 'a reddish-brown metal B.'

Substance B is divided into two parts, each placed in separate test tubes.

Dilute HCl is added to one part of substance B and dilute HNO₃ to the other.

(a) Name the substances A and B.

(b) Give two tests for the colourless liquid formed in the experiment.

(c) What happens to substance A when it reacts with hydrogen ? Give reasons for your answer.

(d) Write an equation for the reaction between hydrogen and substance A.

(e) Is there any reaction between substance B and dilute hydrochloric acid ? Give reasons for your answer.

Helium is preferred to hydrogen for filling balloons because it is

1. lighter than air
2. almost as light as hydrogen
3. non-combustible
4. inflammable

A metal oxide that is reduced by hydrogen is:

1. Al₂O₃
2. CuO
3. CaO
4. Na₂O

Which of the following statements about hydrogen is incorrect ?

1. It is an inflammable gas
2. It is the lightest gas.
3. It is not easily liquefied.
4. It is a strong oxidizing agent.