Mole of A = 0.01 Kmol Total Mol Assumed = Nt So Xa = 0.01/Nt = a (assumed)
Mole of B = Nt-0.01 So Xb = (Nt-0.01)/Nt = (1-a) (Accordingly)
We Know that Y= 4.5X/(1+3.5X) (relative volatilty given 4.5)
Put the assumed value of Xa & Xb in above Eq. & get Ya & Yb
Then Ya+Yb=1 So find the value of a
Now a = .25 (calculated) so 1-a= 0.75 ( that is Xb Ans.)