Răspuns:
M,H2O= 18g/mol
niu=m/M=36/18 mol= 2mol
1mol...contine ,..... N,A= 6,022X10²³ (numarul lui Avogadro) molecule
2mol................N= 12,044X10²³molecule
1sec...........2molecule
x....................12,044x10²³molecule
x=t= 6,022x10²³ secunde
1an are 365zile...365x24 ore....365x24x3600sec=3,15x10⁷sec
t,ani= 6,022x10²³/3,15x10⁷=aproximativ 2x10¹⁶ani
xplicație: