The crystal lattice energy of KI is -677 kJ/mol. The enthalpy of hydration (enthalpy of solvation in water) is -657 kJ/mol.Calculate DeltaHsolution for KI
The Correct Answer and Explanation is :
To calculate the enthalpy of solution ((\Delta H_{\text{solution}})) for potassium iodide (KI), we can use the following equation:
[
\Delta H_{\text{solution}} = \Delta H_{\text{hydration}} + \Delta H_{\text{lattice}}
]
Where:
- (\Delta H_{\text{hydration}}) is the enthalpy of hydration (enthalpy of solvation in water).
- (\Delta H_{\text{lattice}}) is the lattice energy of KI.
Given:
- (\Delta H_{\text{hydration}} = -657 \, \text{kJ/mol})
- (\Delta H_{\text{lattice}} = -677 \, \text{kJ/mol})
Calculation:
Now, substitute the given values into the equation:
[
\Delta H_{\text{solution}} = (-657 \, \text{kJ/mol}) + (-677 \, \text{kJ/mol})
]
[
\Delta H_{\text{solution}} = -657 \, \text{kJ/mol} – 677 \, \text{kJ/mol}
]
[
\Delta H_{\text{solution}} = -1334 \, \text{kJ/mol}
]
Thus, the enthalpy of solution for KI is (-1334 \, \text{kJ/mol}).
Explanation:
The enthalpy of solution represents the overall heat change when a solute dissolves in a solvent. It is the sum of the lattice energy (energy required to break the ionic bonds in the solid lattice) and the enthalpy of hydration (energy released when ions are surrounded by water molecules and stabilized).
- The lattice energy is negative because energy is released when the ionic lattice is formed. A large negative value (-677 kJ/mol) indicates that a significant amount of energy is required to break the ionic bonds in the crystal structure of KI.
- The enthalpy of hydration is also negative, meaning that energy is released when KI dissociates into its ions and the ions are stabilized by the water molecules. The value of (-657 \, \text{kJ/mol}) indicates that hydration releases a considerable amount of energy.
In this case, the overall enthalpy of solution is negative ((-1334 \, \text{kJ/mol})), indicating that the dissolution of KI in water is exothermic, releasing heat into the surroundings.