Question

$X$ and $Y$ both are soluble in given solvent. Molar mass of the polymer $Y$ is

• A. $210gmo{l}^{-1}$
• B. $50gmo{l}^{-1}$
• C. $205gmo{l}^{-1}$
• D. $100gmo{l}^{-1}$

Answer 1

Answer: (B)

From $I$ and $II$,

${\left(\Delta T_b\right)}_x=\frac{1000K_b{w}_1}{m_1{w}_2}$

$5^{\circ }=K_b$ (molality)

$\therefore K_b($ solvent $)=5^{\circ }mo{l}^{-1}kg$

From $I$ and $III$,

${\left(\Delta T_b\right)}_y=10^{\circ }$

$\therefore {\left(\Delta T_b\right)}_y=\frac{1000K_b{w}_1}{m_1{w}_2}$

$\therefore m_1(Y)=\frac{1000K_b{w}_1}{{\left(\Delta T_b\right)}_y{w}_2}$

$=\frac{1000\times 5\times 10}{10\times 100}$

$=50gmo{l}^{-1}$