Question

What is the molality of a solution of citric acid in 50g of acetic
acid has a boiling point elevation of 2.76K. if kb for acetic
acid is 6.07 Kkg/mol?
a) 0.573 mol/kg
b) 0.454 mol/kg
c) 0.354 mol/kg
d) 0.604 mol/kg​

Answer 1

Given :

Elevation of boiling point = 2.76K

Value of Kb = 6.07 K kg/mol

To Find :

Molality of the solution.

Concept :

★ Elevation of boiling point :

• Solution has lower vapour pressure and hence higher boiling point than pure solvent.
• The increase in the boiling point is known as elevation of boiling point.
• For dilute solutions, $\underline{\boxed{\tt{\orange{\Delta T_b=K_b\times m}}}}$

where m is molality of solution and Kb is called boiling point elevation constant or molal elevation constant or Ebullioscopic constant, having unit K kg/mol

Calculation :

$:\implies\tt\:\Delta T_b=K_b\times m$

$:\implies\tt\:2.76=6.07\times m$

$:\implies\tt\:m=\dfrac{2.76}{6.07}$

$:\implies\:\underline{\boxed{\bf{\purple{m=0.454\:mol/kg}}}}$

Answer 2

Given :

Elevation of boiling point = 2.76K

Value of Kb = 6.07 K kg/mol

To Find :

Molality of the solution.

Concept :

★ Elevation of boiling point :

Solution has lower vapour pressure and hence higher boiling point than pure solvent.

The increase in the boiling point is known as elevation of boiling point.

For dilute solutions, $\underline{\boxed{\tt{\orange{\Delta T_b=K_b\times m}}}}$

where m is molality of solution and Kb is called boiling point elevation constant or molal elevation constant or Ebullioscopic constant, having unit K kg/mol

Calculation :

$:\implies\tt\:\Delta T_b=K_b\times m$

$:\implies\tt\:2.76=6.07\times m$

$:\implies\tt\:m=\dfrac{2.76}{6.07}$

$:\implies\:\underline{\boxed{\bf{\purple{m=0.454\:mol/kg}}}}$