Question

What substance is oxidized in the reaction MgO + Cu → Mg + CuO?

Mg, because it lost electrons
Mg, because it gained electrons
Cu, because it lost electrons
Cu, because it gained electrons

Answer 1

In the reaction \( \text{MgO} + \text{Cu} \rightarrow \text{Mg} + \text{CuO} \), we need to determine which substance is oxidized.

In this reaction:

- Magnesium oxide (MgO) contains magnesium in the +2 oxidation state and oxygen in the -2 oxidation state.
- Copper (Cu) is in its elemental form (0 oxidation state) and is reduced when it gains electrons.
- Magnesium (Mg) is produced from magnesium oxide, meaning magnesium is reduced in this case (as it goes from +2 in MgO to 0 in elemental Mg).

However, for copper (Cu) to form copper oxide (CuO), it must have been oxidized (it goes from 0 to +2 oxidation state):

- Copper (Cu) loses electrons during this process.

Thus, the correct answer is:

**Cu, because it lost electrons.**