Question

What is the boiling point elevation constant, Kb, of diethyl ether if 38.2 g of the nonelectrolyte benzophenone, C6H5COC6H5, dissolved in 330. g of diethyl ether produces a solution that boils at 35.7°C? Use molar masses with at least as many significant figures as the data given.

Answer 1

Answer: the boiling point elevation constant is $1.73^0C/m$

Explanation:

Elevation in boiling point is given by:

$\Delta T_b=i\times K_b\times m$

$\Delta T_b=T_b-T_b^0=$ = Elevation in boling point

i= vant hoff factor = 1 (for non electrolyte)

$K_b$ =boiling point constant = ?

m= molality

$\Delta T_b=i\times K_b\times \frac{\text{mass of solute}}{\text{molar mass of solute}\times \text{weight of solvent in kg}}$

Weight of solvent (diethylether)= 330 g = 0.33 kg

Molar mass of solute (benzophenone)= 182 g/mol

Mass of solute (benzophenone) = 38.2 g

$(35.7-34.6)^0C=1\times K_b\times \frac{38.2g}{182g/mol\times 0.33kg}$

$K_b=1.73^0C/m$

Thus the boiling point elevation constant is $1.73^0C/m$