What volume of oxygen is generated by the decomposition of 136 g of potassium permanganate when it is heated?

1. We write down the reaction equation for the decomposition of potassium permanganate:

2KMnO4 = K2MnO4 + MnO2 + O2;

2.Calculate the chemical amount of potassium permanganate:

n (KMnO4) = m (KMnO4): M (KMnO4);

M (KMnO4) = 39 + 55 + 4 * 16 = 158 g / mol;

n (KMnO4) = 136: 158 = 0.86 mol;

3. according to the reaction equation, the amount of oxygen is half the amount of permanganate:

n (O2) = n (KMnO4): 2 = 0.86: 2 = 0.43 mol;

4.find the volume of formed oxygen:

V (O2) = n (O2) * Vm = 0.43 * 22.4 = 9.63 dm3.

Answer: 9.63 dm3.