Question

Se ard 20g calciu.peste oxidul rezultat se adauga 500g apa . Ce concentratie va avea solutia obtinuta?
Se Dau :
A indice Ca ( Aca) =40 A indice H (AH) =32 Si A indice N (An) = 16

Answer 1

M,Ca= 40g/mol

n(niu)= 20g/40g/mol= 0,5mol
1mol..........................1mol
Ca+  1/2O2------> CaO
0,5mol......................0,5mol

1mol.....1mol.......1mol
CaO+ H2O---> Ca(OH)2
0,5mol...0,5mol.....0,5mol
m,Ca(OH)2= 0,5molx74g/mol= 37g
m,H2O= 0,5molx18g/mol= 9g

solutia obtinuta contine
md= 37gCa(OH)2 substanta dizolvata inapa
m,apa= m,initial- m,reactionat= 500g-9g=491g

c= mdx100/ms,               unde ms= md+m,apa= 37g+491g=528g
c= 37x100/ 528=....................calculeaza !!!!