A gas cylinder of capacity of 20 dm³ is filled with gas X the mass of which is 10 g. When the same cylinder is filled with hydrogen gas at the same temperature and pressure the mass of the hydrogen is 2 g, hence the relative molecular mass of the gas is :

1. 5
2. 10
3. 15
4. 20

The vapour density of carbon dioxide [C = 12, O = 16] is

1. 32
2. 16
3. 44
4. 22

Find the total percentage of oxygen in magnesium nitrate crystals : Mg(NO₃)₂. 6H₂O

[O = 16, N = 14, H = 1, Mg = 24]

What is the mass of nitrogen in 1000 kg of urea [CO(NH₂)₂].

[C = 12] (Answer to the nearest kg.)