Another 5 g of sodium chloride was dissolved in 160 g of a 12% sodium chloride solution. What is the mass fraction of salt in the resulting solution?
Given: m (solution) = 160 g, ω (NaCl) = 12%, or 0.12, m1 (NaCl) = 5 g.
Find: ω2 (NaCl) -?
1. Find the mass of the solute (NaCl) in the initial solution:
m (NaCl) = m (solution) • ω (NaCl) = 160 g • 0.12 = 19.2 g.
2. Find the mass of the solute (NaCl) in the resulting solution:
m2 (NaCl) = m (NaCl) + m1 (NaCl) = 19.2 g + 5 g = 24.2 g.
3. Find the mass of the resulting solution:
m2 (solution) = m (solution) + m2 (NaCl) = 160 g + 5 g = 165 g.
4. Find the mass fraction of the solute (NaCl) in the resulting solution:
ω2 (NaCl) = m2 (NaCl) / m2 (solution a) = 24.2 g: 165 g = 0.147, or,
multiplying this value by 100%, we get 14.7%.
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