Which compound will absorb the maximum amount of heat when dissolved in the same amount of water ? (Integral heats of solution at` 25^(@)C` in kcal/mol of each solute are given in brackets)

Options

A. `HCI (Delta H = -17.74)`
B. `HNO_(3)(Delta H = -7.85)`
C. `NH_(4) NO_(3) (Delta H = + 16.8)`
D. `NaCI (Delta H = +1.02)`

Answer

To determine which compound absorbs the maximum amount of heat when dissolved in the same amount of water, we need to analyze the given integral heats of solution at 25°C for each solute.

### Step-by-Step Solution:

1. **Identify the Compounds and Their Heats of Solution**:
- HCl: ΔH = -17.14 kcal/mol (exothermic)
- HNO3: ΔH = -78.85 kcal/mol (exothermic)
- NH4NO3: ΔH = +34.5 kcal/mol (endothermic)
- NaCl: ΔH = +3.87 kcal/mol (endothermic)

2. **Understand the Significance of ΔH**:
- A negative ΔH indicates an exothermic reaction, meaning heat is released when the compound dissolves in water.
- A positive ΔH indicates an endothermic reaction, meaning heat is absorbed when the compound dissolves in water.

3. **Analyze the Compounds**:
- HCl and HNO3 have negative ΔH values, indicating they release heat when dissolved. Therefore, they do not absorb heat.
- NH4NO3 and NaCl have positive ΔH values, indicating they absorb heat when dissolved.

4. **Compare the Positive ΔH Values**:
- For NH4NO3: ΔH = +34.5 kcal/mol
- For NaCl: ΔH = +3.87 kcal/mol
- Since NH4NO3 has a higher positive ΔH value compared to NaCl, it absorbs more heat.

5. **Conclusion**:
- The compound that absorbs the maximum amount of heat when dissolved in the same amount of water is **NH4NO3**.