25 grams of 25% acid solution added 200 grams of water. Calculate the mass fraction of the acid.

Algorithm for solving this problem:
1) Finding the mass of the solute in the solution. To do this, we multiply the mass fraction of the substance by the mass of the solution and divide by one hundred percent.
2) Finding the mass of the solution after adding water. To do this, add the mass of the original solution and the mass of the added water.
3) Calculation of the mass fraction of acid in the resulting solution. For this, the mass of the solute is divided by the mass of the entire solution and multiplied by one hundred percent.
Decision:
1) 25 * 25/100 = 6.25g.
2) 25 + 200 = 225g.
3) 6.25 / 225 * 100 = 2.78% – the answer.