Răspuns: c = 12,85%
Explicație:
concentratia = 100 x masa dizolvata : masa solutiei
c = 100 md / ms
prima solutie :
ms = 500 g, c₁ = 10%
md₁= c x ms₁ : 100 = 10 x 500 : 100 = 50 g
a doua solutie
md₂ = c₂ x ms₂ : 100 = 20 x 200 : 100 = 40 g
in solutia finala exista md = md₁ + md₂ = 50 + 40 = 90 grame
ms = ms₁ + ms₂ = 500 g + 200 g = 700 g
c = 100 x md : ms = 100 x 90 : 700 = 12,85%