132. A solution is obtained by mixing 300 g of 25% solution and 400 g of 40% solution by mass. Calculate the mass percentage of the resulting solution.

Mass of solute in 300 g of solution of 25% conc.
$= \frac{25}{100}\times 300 = 75 \mathrm{g}$
Mass of solvent in 300 g of solution
= 300 – 75 = 225 g Moles of solute in 400 g of solution of 40% conc.
$= \frac{40}{100}\times 400 = 160 \mathrm{g}$
Mass of solvent in 400 g of solution
= 400 – 160 = 240 g Total mass of the solute
= 75 + 160 = 235 g Total mass of solvent
= 225 g + 240 g = 465 g Total mass of solution
= 300 + 400 = 700 g Therefore, composition of solute in solution after mixing = $\frac{235}{700}\times 100 = 33.57\%$
Percentage composition of solvent in solution after mixing
$= \frac{465}{700}\times 100 = 66.43\%$