Question

How to prepare the concentration of 20L .5 molal solution?

Answer 1

Explanation:

C

2

​

H

5

​

OH is 20% by volume i.e. 20 mL of C

2

​

H

5

​

OH is dissolved in 100 mL of solution.

Volume of H

2

​

O=100−20=80 mL

Weight of H

2

​

O=80×1=80 g (d

H

2

​

O

​

=1 g/cc)

Weight of solution =100×0.96=96 g

Weight of C

2

​

H

5

​

OH=96−80=16 g

Molecular weight of C

2

​

H

5

​

OH=12×2+5+16+1=46 g/mol

M=

Mw

2

​

×V

sol

​

W

2

​

×1000

​

=

46×100

16×1000

​

=3.48M

m=

Mw

2

​

×W

1

​

W

2

​

×1000

​

=

46×80

16×1000

​

=4.35m