What mass of benzene can be obtained from 67.2 liters of acetylene if the yield is 75% of the theoretical?

Let’s execute the solution:

According to the condition of the problem, we write down the equation of the process:
2C2H2 = C6H6 – trimerization, benzene was formed;

Calculations:
M (C6H6) = 78 g / mol;

M (C2H2) = 26 g / mol.

Proportions:
1 mol of gas at normal level – 22.4 liters;

X mol (C2H2) -67.2 liters from here, X mol (C2H2) = 1 * 67.2 / 22.4 = 3 mol;

3 mol (C2H2) – X mol (C6H6);

-3 mol -1 mol from here, X mol (C6H6) = 3 * 1/3 = 1 mol.

We find the mass of the product, taking into account its yield:
m (C6H6) = Y * M = 1 * 78 = 78 g (theoretical weight);

m (C6H6) = 0.75 * 78 = 58.5 g

Answer: benzene weighing 58.5 g was obtained