In 150 g solution with a mass fraction of salt of 12%, 8 g of salt was evaporated.

In 150 g solution with a mass fraction of salt of 12%, 8 g of salt was evaporated. What is the mass of salt in the resulting solution?

The mass of salt in the original solution.
m (salt) = W (salt) • m (solution) / 100% = 12% • 150 g / 100% = 18 g.
The mass of the solution after evaporation of the salt.
m (solution) = m (original solution) – m (salt) = 150 g – 8 g = 142 g.

Salt residue mass.
m (remaining salt) = m (original salt) – m (evaporated salt) = 18 g – 8 g = 10 g
Let us determine the mass fraction of salt after evaporation of the salt from the solution.
W (salt) = m (rest. Salt) / m (solution) • 100% = 10 g / 142 g • 100% = 7%.