Question

A mixture of two immiscible liquids A and B,having vapour pressure in pure state obeys the following relationship if ${\chi }_A$ and ${\chi }_B$ are mole fractions of A and B in vapour phase over the solution

• A. $P_A^{{}^{\prime }}=P_M{\chi }_A^{{}^{\prime }}$
• B. $\frac{P_A^{{}^{\prime }}}{P_B^{{}^{\prime }}}=\frac{W_A\times M{w}_B}{M{w}_A\times W_B}$
• C. If $P_A^{{}^{\prime }}>P_B^{{}^{\prime }}$ then ${\chi }_A^{{}^{\prime }}<{\chi }_B^{{}^{\prime }}$
• D. If $P_A^{{}^{\prime }}>P_B^{{}^{\prime }}$ then $n_A>n_B$

Answer 1

Answer: (A), (B), (D)

The correct options are
A $P_A^{{}^{\prime }}=P_M{\chi }_A^{{}^{\prime }}$
B $\frac{P_A^{{}^{\prime }}}{P_B^{{}^{\prime }}}=\frac{W_A\times M{w}_B}{M{w}_A\times W_B}$
D If $P_A^{{}^{\prime }}>P_B^{{}^{\prime }}$ then $n_A>n_B$

For immiscible liquids
$P_A^{{}^{\prime }}=P_M\cdot {\chi }_A^{{}^{\prime }};P_B^{{}^{\prime }}=P_M\cdot {\chi }_B^{{}^{\prime }}$

$\therefore \frac{P_A^{{}^{\prime }}}{P_B^{{}^{\prime }}}=\frac{{\chi }_A^{{}^{\prime }}}{{\chi }_B^{{}^{\prime }}}=\frac{n_A}{n_B}=\frac{W_A\times M{w}_B}{M{w}_A\times W_B}$

If $P_A^{{}^{\prime }}>P_B^{{}^{\prime }}$ then $n_A>n_B$

Hence, options $A,B$ and $D$ are correct