How much water should 40 g of potassium bromide be dissolved to obtain a 15% solution?

The mass of potassium bromide is 40 g.

W = 15%.

Let’s determine the mass of water to be taken. We write down the solution.

For the solution we use the following formula.

W = m r.v. / m r-ra * 100%.

m solution = m H2O + m r.v.

Let’s denote the mass of water through x. Next, we write down an expression with one unknown.

15 = 40 / (x + 40) * 100.

15 = 4000 / (x + 40).

15x + 600 = 4000.

15x = 4000 – 600.

15x = 3400.

Let’s define the unknown value of x.

X = 227 g.

Answer: therefore, in order to obtain this solution, 227 g of water are required.