Zn + 2 HCl => ZnCl2 + H2
masa molara a sarii (ZnCl2) = 65 + 2*35.5 = 136 g/mol
65 g Zn.........136 g ZnCl2
6 g Zn...............x g ZnCl2
x = 136*6/65 = 12.553 g
2*36,5 g HCl.........136 g ZnCl2
y g HCl.................12,553 g ZnCl2
y = 12,553*2*36.5/136 = 6.738 g HCl
40 - 6,738 = 33.262 g HCl => acidul clorhidric este in exces cu 33,262 g
