Answer:
Cl element reduced
ClO₃⁻ oxidizing agent
Fe element oxidized
Fe²⁺ reducing agent
Step-by-step explanation:
Let's consider the following redox reaction.
ClO₃⁻ + Fe²⁺ + 2 H⁺ ⇄ ClO₂ + Fe³⁺ + H₂O
Cl has the oxidation number (o.n.) +5 in ClO₃⁻ and +4 in ClO₂, so Cl is the element reduced according to the following reduction half-reaction.
2 H⁺ + ClO₃⁻ + 1 e⁻ ⇒ ClO₂ + H₂O
As a consequence, ClO₃⁻ is the oxidizing agent.
Fe has the o.n. +2 in Fe²⁺ and +3 in Fe³⁺, so Fe is the element oxidized according to the following oxidation half-reaction.
Fe²⁺ ⇒ Fe³⁺ + 1 e⁻
As a consequence, Fe²⁺ is the reducing agent.