What is the reducing agent in the following reaction: 2Mg + O2 → 2MgO?

O

Mg

Mg and O

Neither element

Mg.

Explanation:

The reducing agent is the agent that is oxidized (losses electrons). The oxidizing agent is the agent that is reduced (gains electrons).

For the mentioned reaction:

2Mg + O₂ → 2MgO.

Mg (oxid. no. = 0) is converted to MgO (oxid. no. of Mg = + 2), which means that Mg losses 2 electrons and is oxidized.

So, the reducing agent is Mg.