Question

1.Calculati numarul de moli apa din formula CaSO4*xH2O, care conține 20,93% H2O.

2. Aflați c%=? ,
Solutie CuSO4
50g CuSO4*5H2O
0,350kg apa

Answer 1

1. Mcristalohidrat = 136+18x g/mol
M sare anhidra = 136g/mol

%H2O = mH2O/Mcristalohidrat×100

20,93 = 18x/136+18x×100
20,93(136+18x) = 1800x
2846,48+376,74x = 1800x
1423,26x = 2846,48
x = 2

F.M => CaSO4×2H2O
nr moli H2O = 2

2. Mcristalohidrat = 160+90 = 250g/mol

250g cris.....160g CuSO4........90g H2O
50g crist.....xg..............................yg

x = 32g CuSO4 (md)
y = 18g H2O

ms final = 32+18+350 = 400g sol. CuSO4×5H2O

C = md/msf×100 = 32/400×100 = Calculeaza !