Evaporation of 345 g of a 10% salt solution gave a solution with a mass fraction of salt of 14%.

Evaporation of 345 g of a 10% salt solution gave a solution with a mass fraction of salt of 14%. What is the mass of the evaporated water?

To start the task, we will find exactly how much pure salt is contained in our solution with a concentration of 10%:
m = 345 grams * 0.1 = 34.5 grams
To find how much water has evaporated, replace the mass of the solution in the formula as the sum of the masses of the solute and the mass of the solvent:
w = mr.v./ (m.v. + mr-la)
The mass of the solute is 34.5 grams.
0.14 = 34.5 / (34.5 + x)
Where: 34.5 = 0.14 * (34.5 + x)
34.5 = 4.83 + 0.14 * x
0.14 * x = 89.67
x = 211.93 grams
Answer: m water = 211.93 grams