We merged 2 solutions of sulfuric acid, 240 g of 30% and 180 g of 5%.

We merged 2 solutions of sulfuric acid, 240 g of 30% and 180 g of 5%. What was the mass fraction of the acid in the resulting solution?

Given:
m1 solution (H2SO4) = 240 g
ω1 (H2SO4) = 30%
m2 solution (H2SO4) = 180 g
ω2 (H2SO4) = 5%

To find:
ω3 (H2SO4) -?

Decision:
1) m1 (H2SO4) = ω1 * m1 solution / 100% = 30% * 240/100% = 72 g;
2) m2 (H2SO4) = ω2 * m2 solution / 100% = 5% * 180/100% = 9 g;
3) m3 (H2SO4) = m1 + m2 = 72 + 9 = 81 g;
4) m3 solution (H2SO4) = m1 solution + m2 solution = 240 + 180 = 420 g;
5) ω2 (H2SO4) = m3 * 100% / m3 solution = 81 * 100% / 420 = 19.3%.

Answer: Mass fraction of H2SO4 is 19.3%.