Question

An aqueous solution of specific gravity, 16 contains 67.5% of a solute by mass. What will be the percentage by mass of solute in the resulting solution obtained when the original solution is diluted to a density of 1200 kg/m (Assume volume conservation to be valid).​

Answer 1

Explanation:

Assume 100 mL of solution of 67% by mass of specific gravity 1.6 gmL

−1

.

Mass of solution =100×1.6=160g.

Mass of solute =

100

67×160

=107.2g.

Now, consider XgH

2

O is added to it.

Mass of new solution =(160+X)g ...(i)

Also, XgH

2

O means X mL of H

2

O and, thus,

Volume of new solution = (100+X)

Using specific gravity of the solution, the mass of new solution

=(100+X)×1.2=(120+1.2X)g ...(ii)

By Eqs. (i) and (ii), we get

160+X=120+1.2X

X =200 mL or 200 g

% by mass of new solution

=

160+200

107.2

×100=29.78%.

So, the answer is 30.