To 120 g of a solution with a mass fraction of sodium chloride of 10% was added 20 g of water.

univerkov | December 9, 2020 | education

To 120 g of a solution with a mass fraction of sodium chloride of 10% was added 20 g of water. Calculate the mass fraction of salt in the solution.

To 120 g of a solution with a mass fraction of sodium chloride of 10% was added 20 g of water. Calculate the mass fraction of salt in the solution.
NaCl + H2O = HCl + NaOH
w = m (substance) / m (solution) * 100%
1) m (substance) = w / m (solution) * 100%
m (substance) = 10/120 * 100 = 8.3 (g)
2) m2 (solution) = m1 (solution) + m (H2O)
m2 (solution) = 120 + 20 = 140 (g)
3) w = m (substance) / m (solution) * 100%
w (HCl) = 8.3 / 140 * 100 = 6%

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