# The laboratory has a solution with a volume of 300 ml with a mass fraction of acetic acid of 70% and a density

**The laboratory has a solution with a volume of 300 ml with a mass fraction of acetic acid of 70% and a density of 1.07 g / ml. What volume of water with a density of 1 g / ml must be added to the existing solution to obtain a solution with a mass fraction of acid of 30%? Disregard the change in volume when mixing the solution and water.**

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

The mass of the solution is 300 x 1.07 = 321 grams;

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

m acid = 321 x 0.7 = 224.7 grams;

To find the mass of water, you need to subtract the mass of the acid from the mass of the solution:

m water = 321 – 227.7 = 96.3 grams;

Check: 96.3 + 227.7 = 321;

In the new solution, 224.7 grams of acid will have a mass fraction of 30%.

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

m solution 2 = 224.7 / 0.3 = 749 grams;

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

m water 2 = 749 – 321 = 428 grams:

Check: (96.3 + 428) / 0.7 = 749;