A) CaO (s) + H2O (l) → Ca(OH)2 (s)
B) 2HClO4 (aq) + CaCO3 (s) → Ca(ClO4)2 (aq) + H2O (l) + CO2 (g)
C) SO2 (g) + H2O (l) → H2SO3 (aq)
D) 2Na (s) + 2H2O (l) → 2NaOH (aq) + H2 (g)
E) HCl (aq) + NaOH (aq) → NaCl (aq) + H2O (l)
Choice D shows Na donating electrons to the H+ in the water molecule and REDUCING its charge from plus one down to zero.
Na goes from zero charge as an element to a plus one charge as a Na+ ion (has been oxidized) H+ goes from plus one charge to zero as an element. (has been reduced)Source(s): retired chem teacher USA
The oxidation number of H in 2H2O is 1+. In H2, the oxidation number is 0.
It may be misleading because the reaction is redox, but the hydrogen in reaction D changes oxidation number.Source(s): Medic.