The correct option is Hydrogen.
Explanation
In chemical reactions, oxidation is defined as the gain of oxygen or the loss of hydrogen by a substance. Conversely, reduction is defined as the loss of oxygen or the gain of hydrogen. Reactions where both oxidation and reduction occur simultaneously are termed redox reactions.
Analysis of the Reaction:
The chemical equation for the reduction of copper(II) oxide by hydrogen is:
CuO + H2 → Cu + H2O
- Copper(II) oxide (CuO): This compound loses oxygen to become copper (Cu). The loss of oxygen constitutes reduction. Therefore, CuO is reduced.
- Hydrogen (H2): This element gains oxygen to form water (H2O). The gain of oxygen constitutes oxidation. Therefore, Hydrogen is oxidised.
Key Takeaway:
The substance that gains oxygen during a reaction is said to be oxidised, while the substance that loses oxygen is said to be reduced.