Question

35. If mole fraction of a solute in benzene is 0.2,
then the vapour pressure of this solution wil
be (given that vapour pressure of pure
benzene is 500 mm of Hg)
(1) 450 mm of Hg
(2) 425 mm of Hg
(3) 400 mm of Hg
(4) 300 mm of Hg
A non ideal solution won nie​

Answer 1

Answer:

CHEMISTRY

The vapour pressure of pure benzene at 50

o

C is 268 mm of Hg. How many moles of non-volatile sohite per mole of benzene are required to prepare a solution of benzene having a vapour pressure 167 mm of Hg at 50

o

C?

November 22, 2019avatar

Maanu Parekh

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ANSWER

Applying Raoult's law in the following form:

P

s

P

0

−P

s

=

Wm

wM

=

W/M

w/m

= No. of moles of solute per mole of benzene

or

N

n

=

167

(268−167)

=0.6047=0.605

Alternative method: We know that, P

s

= Mole fraction of solvent ×P

0

or 167 = Mole fraction of solvent ×268

So, Mole fraction of solvent =

268

167

=0.623

Mole fraction of solute =1−0.623=0.377

N

n

=

Mole fraction of solvent

Mole fraction of solute

=

0.623

0.377

=0.605

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