To 140 g of a solution with a mass fraction of sodium chloride of 15% was added 20 ml of water and 19 g of the same salt. Mass fraction of salt in the resulting solution is equal to
ω = m (substance) / m (solution)
Find the mass of the substance m = 140 * ω + 19 = 40 g
Find the mass of the solution m = m (initial) + m (added) = 140 + 20 + 19 = 179 g
ω (final) = 40 * 100/179 = 22%
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