Question

Calculate the molality of a solution containing 16.5 grams naphthalene (C10H8) in 54.3 grams benzene (C6H6). Molar mass of naphthalene = 248 g/mol.

Answer 1

The mass of naphthalene (solute) in 1 kg (or 1000 g) of benzene (solvent) equals

$m=\frac{16.5\times1000}{54.3}=$ $304g$

Moles of naphthalene:

$n=\frac{304g}{248g/mol}=1.23 mol$

Therefore, the molality equals 1.23 m

Answer: 1.23 m