Question

$1.0$ molal aqueous solution of an electrolyte $X_{3}Y_{2}$ is 25% ionized. The boiling point of the solution is $(K_{b}$ for $H_{2}O= 0.52\, K\, kg/mol)$

• A. $375.5\, K$
• B. $374.04 \,K$
• C. $377.12 \,K$
• D. $373.25\, K$

Answer 1

Answer: (B)

$\underset{1-\alpha}{{x_{3}y_{2}}} \rightleftharpoons \underset{n \alpha}{{3x^{2+}}}+\underset{m\alpha}{{2y^{3-}}}$ for complete ionization,
$i=1+(m+n-1) \alpha$
$i=1+(2+3-1)\times 0.25=1+1=2$
$\Delta\,T_{b}=i\times Kb \times m=2\times 0.52\times 1=1.04$
B.P. of solution $(T_{b})=\Delta\,T_{b}+T^{\circ}_{b}=1.04+373$
$=374.04\,K$