In which reaction does the oxidation number of hydrogen change?
HCl (aq) + NaOH (aq) ? NaCl (aq) + H2O(l)
SO2(g) + H2O(l) --> H2SO3(aq)
2HClO4(aq) + CaCO3(s) --> Ca(ClO4)2(aq) + H2O(l) + CO2(g)
CaO(s) + 2H2O(l) --> Ca(OH)2(s)
2Na(s) + 2H2O(l) --> 2NaOH(aq) + H2(g)