Find the mass of water and citric acid required to prepare 150 g of a 5% solution.

Given: ω (citric acid) = 5%, or 0.05, m (solution) = 150 g.
Find: m (citric acid) – ?, m (water) -?
Decision.
1. Find the mass of the dissolved substance (citric acid) in the solution:
m (citric acid) = m (solution) • ω (citric acid) = 150 g • 0.05 = 7.5 g.
2. Find the mass of the solvent (water):
m (water) = m (solution) – m (citric acid) = 150 g – 7.5 g = 142.5 g.
Answer: m (citric acid) = 7.5 g; m (water) = 142.5 g.