A stable compound has ........... Enthalpy of formation.

Explanation

To determine the enthalpy of formation of a stable compound, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Enthalpy of Formation**:
- The enthalpy of formation (ΔH_f) of a compound is defined as the change in enthalpy when one mole of the compound is formed from its elements in their standard states.

2. **Exothermic vs. Endothermic Reactions**:
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