Question

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.

August 4, 2024

Answer

2KMnO₄ ⟶ K₂MnO₄ + MnO₂ + O₂

Loss in mass = 1.32 g = 1 lit of oxygen

Vapour density of gas = $1.32\over 0.0825$ = 16 g

Molecular weight = 2 × Vapour density

= 2 × 16 = 32 g

Hence, relative molecular mass of oxygen is 32 g

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