To 200 g of a 20% sodium sulfate solution was added 50 g of water. The mass fraction of Na2SO4

To 200 g of a 20% sodium sulfate solution was added 50 g of water. The mass fraction of Na2SO4 in the resulting solution is ..

Given:

m (solution) = 200 g,

W = 20%,

m (water) = 50 g.

m (substances) -?

Decision :

Find the mass of sodium sulfate in the solution.

W = m (substance): m (solution) × 100%, hence

m (substance) = (m (solution) × W): 100%.

m (substance) = (200 g × 20%): 100% = 40 g.

Find the mass of the solution after adding water.

m (solution) = m (water) + m (substance).

m (solution) = 200 g + 50 g = 250 g.

Let’s find the mass fraction of the substance in the resulting solution.

W = (40: 250) × 100% = 16%.

Answer: 16%.