To 200 g of a solution, the mass fraction of the substance in which is 0.3, was added 100 g of water.

To 200 g of a solution, the mass fraction of the substance in which is 0.3, was added 100 g of water. Calculate the mass fraction of the solute in the resulting solution.

Answer: 20%.
Explanation of the solution to the problem: to solve this problem, you must use the following formula:
w = m (solv.v-va) / m (solution), where w is the mass fraction of the solute in the solution, m (solv.v-va) is the mass of the solute, m (solution) is the mass of the solution …
First, we find the mass of the solute:
m (solution in-va) = w * m (solution) = 0.3 * 200 = 60 g.
Further, using the formula presented above, we find the mass fraction of the resulting solution:
w = m (solution in-va) / m (solution) = 60 / (200 + 100) = 0.2.