Question

1.Intr-un litru de apa (densitate= 1g/cm cub) se dizolva 307,5 g sare amara (MgSO4 * 7H2O) . calculati compozitia procentuala a solutiei obtinute .
2. Indicati volumul de apa (densitate= 1g/cm cub) ce trebuie adaugat peste 500g piatra vanata (CuSO4 * 5H2O) pentru a obtine o solutie de concentratie 25% .

Answer 1

mH2O= 1000g
MMgSO4*7H2O=120+126=246 G/mol
246gcristolohidrat.....120g sare
307,5g..........................x=150g MgSO4 (md)
ms=1000g+307,5=1307,5g
c=150*100/1307,5=11,47%
2.
MCuSO4*5H2O=160+90=250g/mol
250g Cristalohidrat........160g CuSO4
500g ch.............................y=320g CuSO4 (md)      ms=320*100/25=1280 g
ms=500+mH2O  ==:mH2o=ms-500=1280-500=780g 
VH2O=m/p=780g/1g/ml=780ml