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Indicati volumul de apa (ρ=1 g/cm³) ce trebuie adaugat peste 500g piatra vanata (CuSO4•5H2O) pentru a obtine o solutie de concentratie 25%

Răspuns :

M, cristalohidrat=(64gCu+32gS+4x16gO)+5x18gH20=250g
M,sare anhidra= 160g CuSO4
250gcristalohidrat............160g sare anhidra..........90gapa
500g................................m=320g.......................m= 180g

concentratia se exprima in sare anhidra, deci md=320g
ms= md+mapa cristalohidrat+ m,apa adugata= 500+ m,apa adaugata
c/100= md/ms,    25/100= 320/(500+m,apa adugata)-----.> CALCULEAZA m,apa !!!!!.