Question

A solution of 2.5 g of a non-volatile solid in 100 g benzene is boiled at 0.42°C higher than the boiling point of pure benzene. Calculate the molecular mass of the substance. Molal elevation constant of benzene is 2.67 K.kg.mol⁻¹ *
(a) 158.9 g/mol
(b) 198.9 g/mol
(c) 178.7 g/mol
(d) 178.9 g/mol​

Answer 1

Explanation:

ANSWER

M=

W×△T

1000K

b

×w

Given,

K

b

=2.67 K.kg.mol

−1

,

w=2.5 g,

W=100 g,

△T=0.42K

Now,

M=

100×0.42

1000×2.67×2.5

=158.9

The molecular weight of substance is 158.9 g/mol