15 grams of sugar was added to 100 g of a 25% sugar solution. What is the mass fraction of sugar

15 grams of sugar was added to 100 g of a 25% sugar solution. What is the mass fraction of sugar in the resulting solution?

Given: the mass of the solution is 100 grams. The concentration of the solution (w) is 25%. The mass of sugar is 15 grams.

Decision:

1) Find the mass of sugar in 100 grams of solution. To do this, subtract 25% from 100%: 100 – 25 = 75%.

2) Find the mass of sugar m = 100 – (100 * 75/100) = 25 g.

3) After adding another 15 grams, it turned out 25 + 15 = 40 grams of sugar.

4) The mass of the solution and sugar is 100 + 15 = 115 g.

5) After that, we find the mass fraction of sugar:

w = 40/115 = 0.35. If you express this number as a percentage, you get 0.35 * 100 = 35%.

Answer: 35%.