To 100 g of a solution with a mass fraction of sodium chloride of 15% was added 35 ml of water and 25 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 = 100 * ω + 25 = 100 * 15 + 25 = 40 g
Find the mass of the solution m = m (initial) + m (added) = 100 + 35 + 25 = 160 g
ω (final) = 40 * 100/160 = 25%
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