The laboratory has 250 g of 2% potassium iodide solution. How much salt should

The laboratory has 250 g of 2% potassium iodide solution. How much salt should be added to increase the concentration to 20%?

Find the mass of salt and water in the original solution.

The mass of the solution is 250 grams;

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

m salt = 250 x 0.02 = 5 grams;

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

m water = 250 – 5 = 245 grams;

Check: 245 + 5 = 250;

In the new solution, 245 grams of water will have a mass fraction of 80%.

Let’s find the mass of this solution by dividing the mass of water by its new mass fraction

m solution 2 = 245 / 0.8 = 306.25 grams;

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

m salt 2 = 306.25 – 250 = 56.25 grams;

Check: (5 + 56.25) / 0.2 = 306.25;