How much water must be evaporated from 350 g of a 12% salt solution to get a 20% solution?

Determine the initial mass of salt in the solution.

To do this, we multiply the known weight of the solution by the salt content in it.

Will be:

350 * 12% = 350 * 0.12 = 42 grams.

Let’s find a new weight of the solution, in which the salt content is 20%.

To do this, we divide the previously found salt mass by the new concentration.

Will be:

42/20% = 42 / 0.2 = 210 grams.

From this it follows that you need to evaporate:

350 – 210 = 140 grams of water.

Answer: 140 grams of water must be evaporated from the initial solution.