Question

40 gm of NAOH dissolves in 180gm of water what is the mole fraction of water in solution

Answer 1

Mass of NaOH=4 g

Number of moles of NaOH=

40 g

4 g

=0.1 mol

Mass of H

2

O=36 g

Number of moles of H

2

O=

18 g

36 g

=2 mol

Mole fraction of water =

No. of moles of water+No. of moles of NaOH

Number of moles of H

2

O

=

2+0.1

2

=

2.1

2

=0.95

Mole fraction of NaOH =

No. of moles of NaOH+No. of moles of water

Number of moles of NaOH

=

2+0.1

0.1

=

2.1

0.1

=0.047

Mass of solution = mass of water + mass of NaOH=36g+4 g=40 g

Volume of solution =40×1=40 mL.

( Since specific gravity of solution is =1 g mL

−1

)

Molarity of solution =

Volume of solution in litre

Number of moles of solute

=

0.04 L

0.1 mol NaOH

=2.5 M

please mark as