
Answer
Energy Diagram for the Formation of CH4
The formation of CH4 from graphite and H2 is an exothermic reaction:
ΔH = –74.8 kJ mol⁻¹
Therefore, the products must lie 74.8 kJ below the reactants in the energy diagram.
Key Features of the Energy Diagram:
- The diagram should include an activation energy peak.
- There must be a lower plateau for the products compared to the reactants.
- A downward vertical arrow labelled 74.8 kJ should connect the reactants to the products, indicating energy release.
Only Diagram 1 accurately shows all these features.
