Hydrogen and water

2.25     describe the reactions of dilute hydrochloric and dilute sulfuric acids with magnesium, aluminium, zinc and iron

All react to give hydrogen and a solution of the metal salt.  Magnesium is the most reactive, followed by aluminium, zinc, and iron.  We see bubbles of hydrogen gas formed: quickly for Mg and getting slower for the other metals.  All the solutions of the salts formed are colourless, apart from iron.  Iron (II) salts in solution are pale green.  (Note that aluminium has a protective layer of its oxide on the surface and will only react quickly if this is removed first.)

·        With hydrochloric acid, solutions of the metal chlorides are formed:

Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)

2Al(s) + 6HCl(aq) → 2AlCl3(aq) + 3H2(g)            (remember that Al forms a ion with 3+ charge)

Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)

Fe(s) + 2HCl(aq) → FeCl2(aq) + 3H2(g)              (notice that iron (II) chloride is formed here)

·        With sulfuric acid, solutions of the metal sulfates are formed:

Mg(s) + H2SO4(aq) → MgSO4(aq) + H2(g)

2Al(s) + 3H2SO4(aq) → Al2(SO4)3(aq) + 3H2(g)

Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g)

Fe(s) + H2SO4(aq) → FeSO4(aq) + H2(g)           (notice that iron (II) sulfate is formed here)