Question

Answer check

Answer 1

Everything you've said above seems to be correct @Itsokay - The oxygen goes from a 0 oxidation state in the reactants (on the left) to -2 in both of the products (on the right). So, its oxidation number has decreased, meaning it must have gained electrons.

Memory Tip:
Oxidation is Loss (of electrons), Reduction is Gain (of electrons) (OIL RIG)

So, O has been reduced. If something has been reduced, then another species in the reaction must have been oxidised (loss of electrons). Can you spot what that is? (Hint: Oxygen will nearly always have an oxidation state of -2 when bonded to a less electronegative element, except in the case of H2O2).