Solutions

The solution concentration calculator solves mass percent problems: find the concentration, prepare a solution, dilute it, evaporate water, add solute, mix two solutions or find the masses by the cross rule. Every step is shown.

The main formula

w = ^m(solute)/_m(solution) · 100 %,   m(solution) = m(solute) + m(water)

The key idea: dilution and evaporation change the mass of the solution, while the mass of the solute stays the same. When mixing, both the masses of solute and the masses of solutions add up.

The cross rule

To get a solution with fraction w from solutions with w₁ and w₂, take them in the ratio

m₁ : m₂ = (w − w₂) : (w₁ − w)

Water has w = 0 %, a pure substance w = 100 %.

Example. 50 g of water is added to 200 g of a 10 % solution: solute 200 · 0.1 = 20 g, solution 250 g, w = 20 / 250 · 100 % = 8 %.