What is the mass of salt that must be added to 200 g of its 20% solution to obtain a 50% solution of this salt?

Let’s find the mass of salt and water in the original solution.

The mass of the solution is 200 grams;

To find the mass of salt, it is necessary to multiply its mass fraction by the mass of the solution.

m salt = 200 x 0.2 = 40 grams;

To find the mass of water, subtract the mass of salt from the mass of the solution:

m water = 200 – 40 = 160 grams;

Check 1: 160 + 40 = 200;

In the new solution, 160 grams of water will have a mass fraction of 50%.

Find the mass of this solution by dividing the mass of water by its new mass fraction

m solution 2 = 160 / 0.5 = 320 grams;

To obtain such a solution, the following mass of salt must be added to the original solution:

m salt 2 = 320 – 200 = 120 grams:

Check 2: (40 + 120) / 0.5 = 320;