# What mass of salt must be added to 100 g of a 5% solution to make the solution 25%?

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

The mass of the solution is 100 grams;

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

m salt = 100 x 0.05 = 5 grams;

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

m water = 100 – 5 = 95 grams;

Check 1: 95 + 5 = 100;

In the new solution, 95 grams of water will have a mass fraction of 75%.

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

m solution 2 = 95 / 0.75 = 126.67 grams;

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

m salt 2 = 126.67 – 100 = 26.67 grams:

Check 2: (5 + 26.67) / 0.25 = 126.67;

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