To 120 g of a 5% sugar solution, 50 g of sugar was added. Find the mass fraction of the substance in the resulting solution.

Given: m (solution) = 120 g, ω (sugar) = 5%, or 0.05, m0 (sugar) = 50 g.
Find: ω2 (sugar) -?
Decision.
1. Find the mass of the solute (sugar) in the solution:
m (sugar) = m (solution) • ω (sugar) = 120 g • 0.05 = 6 g.
2. Find the mass of the solute in the resulting solution:
mp (sugar) = m (sugar) + m0 (sugar) = 6 g + 50 g = 56 g.
3. Find the mass of the resulting solution:
mp (solution) = m (solution) + m0 (sugar) = 120 g + 50 g = 170 g.
4. Let’s find the mass fraction of the dissolved substance (sugar) in the resulting solution:
ωp (sugar) = mp (soda) / mp (solution a) = 56 g: 170 g = 0.329, or 32.9%.
Answer: ωp (sugar) = 32.9%.