70 g of the solution were mixed with a mass fraction of sodium nitrate of 30% and 130 g of a solution of the same salt with a mass fraction of 20%. Mass fraction of salt in the resulting solution is equal to
ω = m (substance) / m (solution)
Find the mass of the substance m = 70 * 0.3 + 130 * 0.2 = 47 g
Find the mass of the solution m = m (initial) + m (added) = 70 + 130 = 200 g
ω (final) = 47 * 100/200 = 23.5%
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