Mixed 60 g of the solution with a mass fraction of calcium nitrate of 15% and 80 g of a solution of the same salt with a mass fraction of 25%. Mass fraction of salt in the resulting solution is equal to
ω = m (substance) / m (solution)
Find the mass of the substance m = 60 * 0.15 + 80 * 0.25 = 29 g
Find the mass of the solution m = m (initial) + m (added) = 60 + 80 = 140 g
ω (final) = 29 * 100/140 = 20.7%
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