Question

If vapour pressure of two liquids A and B are 100 torr and 140 torr, respectively then total vapour pressure of the solution obtained by mixing 4 moles of A and 6 moles of B would be
O 110 torr
O 115 torr
O 124 torr
O 120 torr​

Answer 1

Answer:

P=PA+PB

pA=100*4/4+6=40

PB=140*6/6+4=84

P=40+84=124torr

ans. 124 torr

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Answer 2

Given:

Vapour pressure of liquid A, Pa = 100 torr

Vapour pressure of liquid B, Pb = 140 torr

No. of moles of A in the solution = 4 moles

No. of moles of B in the solution = 6 moles.

To Find:

Total vapour pressure of the solution, P.

Solution:

P = pA +pB

Mole fraction of A, pA = (100× 4) / (4+6)

= 400/10 = 40 torr

Mole fraction of B, pB = (140 × 6) / (6+4)

= 840/10 = 84 torr

P = 40 + 84 = 124 torr

The total vapour pressure of the solution obtained by mixing 4 moles of A and 6 moles of B would be 124 torr.