Question

Find out the molecular weight of $C_{6}H_{5}COOH$ in the case where, $1.22gC_{6}H_{5}COOH$ is added into the solvent benzene and interpret the result.
In $100g$ benzene, $ΔT_{b}=0.13$ and $k_{b}=2.6Kg/mol$ .

Answer 1

$\Delta \text{T} b = \text{0.13} = \left(\text{2.6}\right) \frac{\text{1.22/M}}{\frac{\text{100}}{\text{1000}}}$
$\text{0.13} = \text{2.6} \times \frac{\text{1.22}}{\text{M}} \text{10}$
$\text{M} = \text{2.6} \times \frac{\text{1.22} \times \text{10}}{\text{0.13}}$
$= \text{244 g/mole}$
This value of molar mass suggest that benzoic acid(C₆H₅ COOH) is dimerised in benzene