Question

At a certain temperature the vapour pressure (in mm hg) of CH3OH and C2H5OH solution is represented bt p=119x+135 where x is the mole fraction of CH2OH, what are the vapour pressure of pure components at this temperature?

Answer 1

Explanation:

Let the vapour pressures of methly alcohol(CH3OH) and ethyl alcohol(C2H5OH) be P1 and P2

Let mole fraction of CH3OH be 'x' and C2H5OH be 'y'

Now, Let total partial pressure be P,

P=P1+P2

=> P= P1(x)+P2(y)

But x+y=1=> y=1-x

Therefore, P=P1x+P2(1-x)

=> P = P1x+P2-P2x

=> P=(P1-P2)x+P2,

Comparing it with P=119x+135, we get P2=135, and

P1-P2=119

=> P1= 119+P2

=> P1= 254

Hence Vapour Pressure of Methly alcohol P1 is 254 bar and Ethyl Alcohol P2 is 135 bar