Determine the freezing point of a solution that contains 78.8 g of naphthalene (c10h8, molar mass = 128.16 g/mol) dissolved in 722 ml of benzene (d = 0.877 g/ml). pure benzene has a melting point of 5.50°c and a freezing point depression constant of 4.90°c/m.0.74°c4.76°c4.17°c1.68°c1. 33°c

0.74°C

Explanation:

The freezing point depression is a colligative property that can be calculated using the following expression.

ΔTf = Kf . b

where,

ΔTf: depression in the melting point

Kf: freezing point depression constant

b: molality

The mass of the solvent (benzene) is:

The moles of solute (naphtalene) are:

The molality of naphtalene is:

ΔTf = Kf . b

ΔTf = (4.90°C/m) . 0.972m = 4.76°C

The melting point of the solution is:

5.50°C - 4.76°C = 0.74°C