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