Question

Which of the following is an oxidising agent in $2Mg+O_2\left(g\right)\to 2MgO\left(s\right)$

• A. Mg
• B. $O_2$
• C. Both Mg and O
• D. None of these

Answer 1

The correct option is B $O_2$

An oxidizing agent or oxidant is a substance which supplies oxygen or any other electronegative element or removes hydrogen or any other electropositive element. Alternatively, an oxidizing agent or oxidant is that substance which itself undergoes reduction in a chemical reaction.
Here Mg is oxidised and $O_2$ is reduced.
Therefore $O_2$ is an oxidising agent.