The reaction between MgO (magnesium oxide) and Ca (calcium) is a metathetical reaction, also known as a double displacement reaction. However, it's important to understand that this reaction requires very high temperatures to proceed.

Here's why:

* MgO is a very stable compound: The ionic bond between magnesium and oxygen is strong.

* Ca is a reactive metal: It readily reacts with oxygen.

The reaction can be represented as follows:

MgO + Ca → Mg + CaO

Here's a breakdown of the reaction:

* Calcium (Ca) is a more reactive metal than magnesium (Mg).

* At high temperatures, calcium will displace magnesium from its oxide, forming calcium oxide (CaO) and leaving behind magnesium (Mg).

Important Note: This reaction is not practical at room temperature or under normal conditions. It requires high temperatures (above the melting point of both calcium and magnesium) to overcome the energy barrier for the reaction to occur.