The mass of benzene, which is necessary to obtain 19.68 g of nitrobenzene, the yield of which is 80%, is _g.

Let’s implement the solution:

In accordance with the condition of the problem, we write down the process:
C6H6 + HNO3 = C6H5NO2 + H2O – nitration, nitrobenzene was formed;

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

M (C6H5NO2) = 118 g / mol.

Let’s determine the amount of the product, if the mass is known:
W = m (practical) / m (theoretical) * 100;

m (C6H5NO2) = 19.68 / 0.80 = 24.6 g;

Y (C6H6NO2) = m / M = 24.6 / 118 = 0.2 mol; Y (C6H6) = 0.2 mol since the amount of these substances is 1 mol.

We find the mass of the original substance:
m (C6H6) = Y * M = 0.2 * 78 = 15.6 g

Answer: you need benzene weighing 15.6 g