Mg + 2HCl = MgCl2 + H2
2 moli HCl.......................1 mol H2
7 moli HCl.......................x=3,5 moli H2
mHCl=7*36,5=255,5g
m H2=3,5*2=7g
1 mol Mg.........2 moli HCl
3,5 moli Mg.......7 moli HCl
2 moli HCl.................1 mol MgCl2
7 moli HCl.................3,5 moli MgCl2