Question

If two substances A and B have $P_A^o:P_B^o=1:2$ and have mole fraction in solution 1 : 2 then mole fraction of A in vapours:

• A. 0.33
• B. 0.25
• C. 0.52
• D. 0.2

Answer 1

Answer: (D)

In an ideal solution of components 'A' and 'B' Mole fraction of component 'A9 in the vapour $Phase=\frac{PartialpressureofA}{Totalvapourpressure}$ $=\frac{P_A}{P_A+P_B}$ $=\frac{P_A^o.x_A^o}{P_A^o.x_A+P_B^o.x_B}$ $=\frac{1\times 1}{1\times 1+2\times 2}$ $=\frac{1}{1+4}=\frac{1}{5}=0.2$