Question

Why oxygen is called reducing agent

Answer 1

If any chemical is an electron donor (reducing agent), another must be an electron recipient (oxidizing agent). A reducing agent is oxidized because it loses electrons in the redox reaction. ... Historically, reduction referred to the removal of oxygen from a compound, hence the name 'reduction'.

Answer 2

If any chemical is an electron donor (reducing agent), another must be an electron recipient (oxidizing agent). Areducing agent is oxidized because it loses electrons in the redox reaction. ... The oxygen (O2) is being reduced, so it is the oxidizing agent.