To 70 g of a 20% solution, 30 g was added. solution of the substance. What is the mass fraction

To 70 g of a 20% solution, 30 g was added. solution of the substance. What is the mass fraction of the substance in the solution?

Problem solving plan:
– calculation of the mass of the solute.
– calculation of the mass of the resulting solution.
-calculation of the mass fraction of a substance in the resulting solution.
Working formula:
W = (mr.v – wa / mr – pa) * 100%.
Decision :
– We express the mass of the solute from the working formula and find it: 20 = (x / 70) * 100.
x = 14g.
– the mass of the resulting solution is the sum of the initial mass of the solution and the mass of the added solution: 70 + 30 = 100g.
-W = (14/100) * 100 = 14g – mass fraction of the substance in the resulting solution.