To a solution of 650 ml with a mass fraction of sodium hydroxide of 40% and a density of 1.44 g / ml

To a solution of 650 ml with a mass fraction of sodium hydroxide of 40% and a density of 1.44 g / ml was added 250 ml of water. Determine the mass fraction of sodium hydroxide in the resulting solution?

1.Let’s find the mass of the NaOH solution.

m = Vp.

m = 650 ml × 1.44 g / ml = 936 g.

2. The mass fraction of a substance in a solution is determined by the formula.

W = m (substance): m (solution) × 100%,

hence m (substance) = (m (solution) × w): 100%.

m (substance) = (936 g × 40%): 100% = 374.4 g.

m (water) = 1 g / ml × 250 ml = 250 g.

m (solution) = 936 g + 250 g = 1186 g.

W = (374.4: 1186) × 100% = 31.57%.

Answer: 31.57%.