Question

Calculate the % degree of dissociation of electrolyte $X{Y}_2$
(Normal mol mass=164) in water if the observed molar mass by measuring elevation in boiling point is $65.6$?

• A. 25
• B. 65
• C. 45
• D. 75

Answer 1

Answer: (D)

75

$A{B}_2⟶A+2B$

$i$= Vant Hoff factor= $1+2d$ ($d$=degree of dissociation)

$i=\frac{\text{Normal mass}}{\text{Observed mass}}=\frac{164}{65.6}=2.5$

$\Rightarrow 1+2d=2.5\Rightarrow d=0.75$, Thus percentage dissociation= $0.75\times 100=75$%