1. We make a chemical equation, not forgetting to put down the coefficients:
2KMnO4 = O2 + K2MnO4 + MnO2.
2. Let’s find the amount of substance oxygen:
n (O2) = V / Vm = 11.2 / 22.4 = 0.5 mol.
3. According to the equation we make up the proportion:
n (O2) / 1 = n (KMnO4) / 2; Therefore: n (KMnO4) = 1 mol.
4. Find the mass of KMnO4:
m (KMnO4) = n * M = 1 * 158 = 158g.
Answer: m (KMnO4) = 158g.
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