Merged two solutions of sulfuric acid: 120 g 40% and 180 g 10%. Find the mass fraction of acid in the resulting solution.

Given: m1 (solution) = 120 g,: ω1 (acid) = 40%, or 0.4, m2 (solution) = 180 g,: ω2 (acid) = 10%, or 0.1.
Find: ω (acid) -?
Decision.
1. Find the mass of the solute (acid) in the first solution:
m1 (acid) = m1 (solution) • ω1 (acid) = 120 g • 0.4 = 48 g.
2. Find the mass of the solute (acid) in the second solution:
m2 (acid) = m2 (solution) • ω2 (acid) = 180 g • 0.1 = 18 g.
3. Find the mass of the solute in the resulting solution:
m (acid) = m1 (acid) + m2 (acid) = 48 g + 18 g = 66 g.
4. Find the mass of the resulting solution:
m (solution) = m1 (solution) + m2 (solution) = 120 g + 180 g = 300 g.
5. Find the mass fraction of the dissolved substance (acid) in the resulting solution:
ω (acid) = m (acid) / m (solution) = 66 g: 300 g = 0.22, or 22%.
Answer: 22%.