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.
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.
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.
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