Answer to Question #328892 in General Chemistry for Sophia

Question

Solve for what is being asked.

What is the molar mass of the solute in a solution made by dissolving 34.41

g of an unknown nonelectrolyte compound in 280.0 g benzene. The boiling point of

the solution is 93.2 °C. Benzene has a boiling point of 80.1 °C and molal boiling-

point elevation constant of 2.53 °C/m.

Answer 1

m(solvent, benzene) = 280.0 g = 0.2800 kg;

m(unknown nonelectrolyte) = 34.41 g;

K_b = 2.53 C/m;

T = 93.2 C

T₀ = 80.1 C;

$\Delta$ T = T - T₀;

$\Delta$ T = K_b * m = K_b * n/m(solvent) = K_b * m(unknown nonelectrolyte)/(M(unknown nonelectrolyte) * m(solvent);

M(unknown nonelectrolyte) = K_b * m(unknown nonelectrolyte)/($\Delta$ T * m(solvent)) = K_b * m(unknown nonelectrolyte)/((T - T₀) * m(solvent)) = 2.53 * 34.41/((93.2-80.1) * 0.2800) = 2.53 * 34.41/(13.1 * 0.2800) = 23.7 g/mol.

Answer: 23.7 g/mol.