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Se dau 200 g solutie soda de rufe,ce concentratie 50%.Cata apa trebuie adaugata pentru a obtine o solutie de 20%?

Răspuns :

C=md/ms*100=>md=50*200/100=100g

ms=md+mH2O=>mH2O=ms-md=200-100=100g

C*mH2O=md(100-C) => mH2O=md(100-C)/C=100(100-20)/20= 400g

mH2O adăugat = 400-100=