120 g of water was added to 350 g of an 11% Na2SO4 solution. Determine the mass fraction

120 g of water was added to 350 g of an 11% Na2SO4 solution. Determine the mass fraction of salt in the resulting solution with an accuracy of 10.

Given:

m (Na2SO4 solution) = 350 g;

w% (Na2SO4) = 11%;

m (H2O) = 120 g;

To find:

w% (Na2SO4 in the final solution) -?

Decision:

1) Find the mass of sodium sulfate in the originally given solution:

m (Na2SO4) = 350 g * 0.11 = 38.5 g;

2) Find the mass of the solution after adding a portion of water:

m (solution) = 350 g + 120 g = 470 g;

3) Find the mass fraction of sodium sulfate in the resulting solution:

w% (Na2SO4) = m (Na2SO4): m (solution) * 100% = 38.5 g: 470 g * 100% = 0.082 * 100% = 8.2%.

Answer: w% (Na2SO4) = 8.2%.