2KMnO₄ ⟶ K₂MnO₄ + MnO₂ + O₂

K₂MnO₄ + MnO₂ is the solid residue.

Potassium permanganate was heated in a test tube. After collecting one litre of oxygen at room temperature, it was found that the test tube had undergone a loss in mass of 1.32 g. If one litre of H₂ under the same conditions of temperature and pressure has a mass of 0.0825 g. Calculate the relative molecular mass of oxygen.

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

Give one word or phrase for : The ratio of the mass of a certain volume of gas to the mass of an equal volume of hydrogen under the same conditions of temperature and pressure.

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

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