Question

Two liquids a and b are mixed in 1 : 4 mole ratio to form an ideal solution. If pure liquid 'a' and 'b' exert a vapour pressure of 75 mmhg and 22 mmhg respectively, the vapour pressure of liquid a in the vapour phase would be

Answer 1

The vapour pressure of a in vapour phase is praportional to its mole fraction 
= 75(1/5)
= 15mmHg

and net vapour pressure of liquid is 
= 15 + 22(4/5)
= 15 + 17.6
= 32.6 mmHg