Find the mass of methane that was burned in 66 liters of oxygen.

To solve the problem, we write down the process equation:

СН4 + 2О2 = СО2 + 2Н2О + Q – methane combustion, heat is released, carbon monoxide (4), water;
Calculations by the formulas of substances:
M (CH4) = 16 g / mol;
M (O2) = 32 g / mol.

3. Proportions:

1 mol of gas at normal level – 22.4 liters;
X mol (O2) – 66 liters from here, X mol (O2) = 1 * 66 / 22.4 = 2.9 mol;

X mol (CH4) – 2.9 mol (O2);
-1 mol -2 mol hence, X mol (CH4) = 1 * 2.9 / 2 = 1.47 = 1.5 mol.

We find the mass of the original substance:
m (CH4) = Y / M = 1.5 * 16 = 24 g

Answer: you need methane weighing 24 g