Liquids A and B form an ideal solution in the entire composition range. At 350 ~K , the vapor pressures of pure A and pure B are 7 10^ 3 ~Pa and 12 10^ 3 ~Pa , respectively. The composition of the vapour is in equilibrium with a solution containing 40 mole percent of A at this temperature is:
B. x_ A =0.28 ; x_ B =0.72
P _ A ^ =7 10^ 3 P _ B ^ =12 10^ 3 x_ A ^ =0.4 ; x_ B ^ =1-0.4 x_ B ^ =0.6 P _ total = P _ A ^ ^ x_ A ^ + P _ B ^ x_ B ^ =7 10^ 3 0.4+12 10^ 3 0.6 =(7 0.4+12 0.6) 10^ 3 =10^ 4 x_ A = P _ A ^ ^ x^ A P _ total = 7 10^ 3 0.4 10^ 4 x_ A =0.28, x_ B =1-0.28=0.72
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