To 200 g of a solution with a mass fraction of potassium nitrate 20%, 75 ml of water and 25 g of the same

To 200 g of a solution with a mass fraction of potassium nitrate 20%, 75 ml of water and 25 g of the same salt were added. The mass fraction of salt in the resulting solution is

Given:

m (solution) = 200 g;

w% (KNO3) = 20%;

m (H2O) = 75 ml = 75 g;

m (salt) = 25 g;

To find:

w% (KNO3 in final solution) =?

Decision:

1) Find the mass of salt in the solution:

m (KNO3) = 200 g * 0.2 = 40 g;

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

m (solution) = 200 g + 75 g = 275 g;

3) Find the mass of salt after adding a portion:

m (KNO3) = 40 g + 25 g = 65 g;

4) Find the mass of the solution after adding salt:

m (solution) = 275 g + 25 g = 300 g;

5) Find the mass fraction of salt in the final solution:

w% (KNO3) = m (KNO3): m (solution) * 100% = 65 g: 300 g * 100% = 21.67%.

Answer: w% (KNO3) = 21.67%.