How many grams of sodium hydroxide should be dissolved in 300 g of a 5% solution to obtain a 10% NaOH solution.

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

The mass of the solution is 300 grams;

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

m salt = 300 x 0.05 = 15 grams;

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

m water = 300 – 15 = 285 grams;

Check: 285 + 15 = 300;

In the new solution, 285 grams of water will have a mass fraction of 90%.

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

m solution 2 = 285 / 0.9 = 316.67 grams;

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

m salt 2 = 316.67 – 300 = 16.67 grams:

Check: (15 + 16.67) / 0.1 = 316.67;