Define `DeltaH`.What will be the sign of `DeltaH` in
(i) exothermic reaction and
(ii) endothermic reaction?

Explanation

**Step-by-Step Solution:**

1. **Definition of ΔH:**
- ΔH represents the change in enthalpy of a system. Enthalpy (H) is a thermodynamic quantity that reflects the total heat content of a system at constant pressure. The symbol Δ (delta) signifies a change in this quantity. Therefore, ΔH is the heat absorbed or released during a process at constant pressure.

2. **Sign of ΔH in Exothermic Reactions:**
- In an exothermic reaction, energy is released into the surroundings. This means that the system loses heat, resulting in a decrease in enthalpy. Therefore, the sign of ΔH for an exothermic reaction is negative (ΔH < 0).
- **Example:** The combustion of carbon in oxygen to form carbon dioxide (C + O2 → CO2) is an exothermic reaction, and it releases heat, leading to a negative ΔH.
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