Question

1 g of a non-volatile non-electrolyte solute is dissolved in 100 g of two different solvents A and B, whose ebullioscopic constants are in the ratio of 1 : 5. The ratio of the elevation in their boiling points, `(Delta T_b (A))/(Delta T_b (B))`, is ______.

Options

• 5 : 1

• 1 : 0.2

• 10 : 1

• 1 : 5

Answer 1

1 g of a non-volatile non-electrolyte solute is dissolved in 100 g of two different solvents A and B, whose ebullioscopic constants are in the ratio of 1 : 5. The ratio of the elevation in their boiling points, `(Delta T_b (A))/(Delta T_b (B))`, is 1 : 5.

Explanation:

Given: Mass of solute = 1 g

Mass of both solvents A and B = 100 g = 0.1 kg

Ebullioscopic constants (boiling point elevation constants) ratio:

`K_b^((A)) : K_b^((B)) = 1 : 5`

ΔT_b = K_b m

= `K_b * (n_"solute")/"mass of solvent in kg"`

Since 

The solute and its mass are the same.

The mass of the solvents is the same.

The elevation in boiling point is directly proportional to K_b.

`(Delta T_b^((A)))/(Delta T_b^((B))) = (K_b^((A)))/(K_b^((B)))`

= `1/5`

= 1 : 5