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Peste 400g solutie NaCl se adauga 200g apa. Concentratia solutiei devine 20%. Concentratia procentuala a solutiei initiale este :

Răspuns :

Ms=400g+200g=600g
c%=[tex] \frac{Md}{Ms}*100 [/tex]
20=[tex] \frac{Md}{600}*100 [/tex]
12000=Md*100
Md=120g=Md2
c%=[tex] \frac{Md2}{Ms2}*100 [/tex]
c%=[tex] \frac{120}{400}*100 [/tex]=30