Question

The vapour pressure of 2.1 of an aqueous solution of non volatile solute at 373k is 755mmhg. Calculate the molar mass of the solute

Answer 1

Explanation:

Let mass of H

2

O be 100g(W

1

)

So mass of non- electrolyte= 2.1g(W

2

)

M

1

=18g M

2

=?

Vapour pressure of solution= 755mm of Hg

Now,

P

o

P

o

−P

=iX, i=1 for non-electrolyte

⇒

760

760−755

=

n

1

+n

2

n

2

≈

n

1

n

2

as n

2

<<n

1

⇒

760

5

=

M

2

×W

1

W

2

×M

1

=

M

2

×100

2.1×18

⇒M

2

=57.456g/mol