What is the basic difference between enthalpy of formation and enthalpy of reaction? Illustrate with suitable examples.

Explanation

To answer the question regarding the basic difference between enthalpy of formation and enthalpy of reaction, we will break down the definitions and provide examples for clarity.

### Step 1: Define Enthalpy of Reaction
The enthalpy of reaction (ΔH_R) is defined as the amount of heat that is either evolved or absorbed during a chemical reaction when the number of moles of reactants, as represented by the balanced chemical equation, have completely reacted.

**Example:**
For the combustion of methane:
\[ \text{CH}_4(g) + 2 \text{O}_2(g) \rightarrow \text{CO}_2(g) + 2 \text{H}_2\text{O}(l) \]
...