What heats the mantle?

Fire

Explanation:

35 KJ.

Explanation:

The activation energy is the minimum energy that must be overcome for a reaction to take place.

In the diagram given above, the activation energy lies between the energy of the reactants and that at the peak.

Thus we can calculate the activation energy as follow:

Energy of reactants = 30 KJ

Energy at the peak = 65 KJ

Activation energy =..?

Activation energy = Energy at the peak – Energy of reactants

Activation energy = 65 – 30

Activation energy = 35 KJ

Therefore, the activation energy of th reaction is 35 KJ