Question

A solution has 1:4 mlar ratio of pentane and
hexane. The vapour pressure of pure hydrocarbons at 20°C a 440 mmhg for pentane
and 120 mm of Hg for hexane.the mole fraction of pentane in vapour phase would be​

Answer 1

answer- Mole fraction of pentane solution=

1+4

1

=

5

1

Mole fraction of hexane solution=

1+4

4

=

5

4

Total pressure of solution, P

S

=X

P

P

P

O

+X

H

P

H

O

=

5

1

×440 mm Hg+

5

4

×120 mm Hg

=184 mm Hg

∴ The fraction of pentane in the vapour phase

=

P

S

X

P

P

P

O

=

184

88

=0.478 .