Balance the following chemical equations:

a. Al(s) + Cl₂(g) → AlCl₃(s)
b. Fe(s) + H₂O(g) → Fe₃O4(s) + H₂(g)
c. Cu(NO₃)₂(aq) + NaOH(aq) → Cu(OH)₂(s) + NaNO₃(aq)