Question

If two substance a and b have pa and pb =1:2 and have mole fraction in solution 1:2 then mole fraction of a in vapour is

Answer 1

Answer:

Explanation:

=> Mole fraction of component in vapour state:

Y = P / P_total

where,

P = partial pressure of component

P_total = total pressure.

=> Therefore,

Y_1 = P_1 / P_total ...(1)

Y_2 = P_2 / P_total ...(2)

By dividing equation (1) by (2), we obtain

Y_1/Y_2 = P_1/P_2 ...(3)

=> Here, Partial pressure of component,

P = x X p^{0}

where,

x = mole fraction of component

p^{0} = partial pressure of component

P_1 = x_1 P1^{0} ...(4)

P_2 = x_2 P2^{0} ...(5)

By dividing equation (3) by (4), we obtain

P_1/P_2 = (x_1 / x_2) X (P_1^{0} / P_2^{0}

=> The value of  (x_1 / x_2) and (P_1^{0} / P_2^{0} is given as 1/2 and 1/2 respectively. Thus,  

P_1/P_2 = 1/4

Place this value in the equation (3),

Y_1/Y_2 = 1/4

= 0.25

Therefore, The mole fraction of A in vapour phase is 0.25