To 150 g of a solution with a mass fraction of magnesium nitrate of 10%, 15 g of the same salt was added and 45 ml of water was evaporated. Mass fraction of salt in the resulting solution is equal to
ω = m (substance) / m (solution)
Find the mass of the substance m = 150 * ω + 15 = 30 g
Find the mass of the solution m = m (initial) + m (added) = 150 + 15 -45 = 120 g
ω (final) = 30 * 100/120 = 25%
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