Chemical reaction: HCl + Ba → BaCl₂ + H₂.
Oxidation reaction: Ba⁰ → Ba⁺² + 2e⁻.
Reduction reaction: 2H⁺ + 2e⁻ → H₂⁰.
Balanced chemical reaction: 2HCl + Ba→ BaCl₂ + H₂.
Barium (Ba) change oxidation number from 0 to +2 (lose electrons), barium is oxidized (reducing agent).
Hydrogen change oxidation number from +1 to 0 (gain electrons), it is reduced.
