From 400 g of a hot 50% salt solution, 80 g of salt crystals precipitated upon cooling. What is the mass fraction of salt in the solution above the precipitate (in%)?
ω = m (substance) / m (solution)
Find the mass of salt m = 400 * 0.5 – 80 = 120 g
Find the mass of the final solution = 400 -80 = 320 g
ω = m (substance) / m (solution) = 120 * 100/320 = 37.5%
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