In the following reaction, state whether O is oxidized or reduced:

Question

1. CH₃CH = 0 → CH₃CH₂OH

Answer 1

The reaction shown is a reduction of an aldehyde to an alcohol.   This is typically done with a reducing agent such as

NaBH4.  The aldehyde is reduced, but the atom within the aldehyde that is gaining the electrons (being reduced) is usually thought of as the being the carbon not the oxygen.