Enthalpy of Solution
1. Include your results and calculations from the practical investigation to determine the enthalpy of solution of some simple ionic compounds.
2. Define the following terms:
a. Lattice formation enthalpy
b. Enthalpy of hydration
c. Enthalpy of solution
Using reaction 1 as an example, include an equation to accompany each of your definitions
3. Calculate the enthalpy of solution of NaCl(s), given the following data:
Enthalpy hydration Na+ = -406 kJ mol-1
Enthalpy hydration Cl- = -364 kJ mol-1
Enthalpy of lattice formation of NaCl(s) = -788 kJ mol-1
4. Draw an energy cycles for reactions 1 and 2 from your experiments to illustrate how the lattice enthalpies of KNO3 and CaCl2 could be calculated using your results if the enthalpies of hydration were known.
Sample Solution
Enthalpy is a state function whose change indicates the amount of heat transferred from a system to its surroundings or vice versa, at constant pressure. The lattice formation enthalpy is the enthalpy change when 1 mole of solid crystal is formed from its scattered gaseous ions. Lattice formation enthalpies are always negative. Enthalpy of hydration is described as the amount of energy released on dilution of one mole of gaseous ions. It can be considered as enthalpy of solvation with the solvent being water. It is also called hydration energy and its values are always negative. The enthalpy of solution is the heat released or absorbed when a specified amount of a solute dissolves in a certain quantity of solvent at constant pressure.
