M, azotat= 24gMg+28gN+96g0= 148g/mol
masa celor 7 moli :
m= n,molxMg/mol----> m= 7molx148g/mol=-------------------------
compozitia procentuala:
148g azotat........24gMg......28gN........96gO
100g..........................x................y.............z
1mol azotat contine 24gMg
2mol.................................m= 2x24g Mg