To 170 g of a 42% salt solution was added 40 ml of water. What is the percentage concentration of the solution?

Given:

m (salt) = 170 g

w% (salt) = 42%

V (H2O) = 40 ml

Find:

w% (salts in the final solution) -?

Solution:

1) Find the mass of salt in the originally given solution:

m (salt) = 170 g * 0.42 = 71.4 g;

2) Find the mass of added water:

m (H2O) = p * V = 1 g / ml * 40 ml = 40 g;

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

m (solution) = 170 g + 40 g = 210 g;

4) Find the mass fraction of salt in the resulting solution:

w% (salt) = m (salt): m (solution) * 100% = 71.4 g: 210 g * 100% = 34%.

Answer: w% (salt) = 34%.