By evaporation of 550 g of a 15% potassium nitrate solution, a solution of 200 g was obtained.

By evaporation of 550 g of a 15% potassium nitrate solution, a solution of 200 g was obtained. Determine the mass fraction of the substance in the resulting solution.

1. Find the mass of potassium nitrate in the original solution, after evaporation it will not change:

m (KNO3) = w (KNO3) * m (1 solution);

m (KNO3) = 0.15 * 550 = 82.5 g;

2.Calculate the mass fraction of nitrate after evaporation:

w (KNO3) = m (KNO3): m (2 solutions);

w (KNO3) = 82.5: 200 = 0.4125 or 41.25%.

Answer: 41.25%.