Oxygen was obtained from potassium permanganate with a mass of 7.9 g, which reacted with magnesium.

Oxygen was obtained from potassium permanganate with a mass of 7.9 g, which reacted with magnesium. What mass of magnesium oxide will be obtained?

Let’s implement the solution:
1. To solve, we compose the equations:
M = 7.9 g;
2KMnO4 = K2MnO4 + MnO2 + O2 – OBP, oxygen is evolved;
X g -?
2Mg + O2 = 2MgO – compounds, magnesium oxide was obtained.
2. Calculations:
M (KMnO4) = 158 g / mol;
M (O2) = 32 g / mol;
M (MgO) = 40.3 g / mol.
3. Determine the amount of the original substance:
Y (KMnO4) = m / M = 7.9 / 158 = 0.05 mol.
4. Proportions:
0.05 mol (KMnO4) – X mol (MgO);
-1 mol -2 mol from here, X mol (MgO) = 0.05 * 2/1 = 0.025 mol.
0.025 mol (О2) –X mol (MgO);
-1 mol -2 mol from here, X mol (MgO) = 0.025 * 2/1 = 0.05 mol.
5. Find the mass of the product:
m (MgO) = Y * M = 0.05 * 40.3 = 2.02 g.
Answer: obtained magnesium oxide weighing 2.02 g.