Two solutions of nitric acid were mixed: 140 g of 10% and 160 g of 25%. Find the mass fraction of acid in the resulting solution.

Given: m1 (solution) = 140 g,: ω1 (acid) = 10%, or 0.1, m2 (solution) = 160 g, ω2 (acid) = 25%, or 0.25.
Find: ω (acid) -?
Decision.
1. Calculate the mass of the solute (acid) in the first solution:
m1 (acid) = m1 (solution) • ω1 (acid) = 140 g • 0.1 = 14 g.
2. Calculate the mass of the solute (acid) in the second solution:
m2 (acid) = m2 (solution) • ω2 (acid) = 160 g • 0.25 = 40 g.
3. Calculate the mass of the solute (acid) in the resulting solution:
m (acids) = m1 (acids) + m2 (acids) = 14 g + 40 g = 54 g.
3. Calculate the mass of the resulting solution:
m (solution) = m1 (solution) + m2 (solution) = 140 g + 160 g = 300 g.
4. Calculate the mass fraction of the solute (acid) in the resulting solution:
ω (acid) = m (acid) / m (solution) = 54 g: 300 g = 0.18, or,
multiplying this value by 100%, we get 18%.
Answer: 18%.