Questions: 3. Specify which compound in the following pairs of ionic compounds has the higher lattice energy. Explain your choice. ( 6 points)
a. KCl or MgO
Transcript text: 3. Specify which compound in the following pairs of ionic compounds has the higher lattice energy. Explain your choice. ( 6 points)
a. KCl or MgO
Solution
Solution Steps
Step 1: Understanding Lattice Energy
Lattice energy is the energy required to separate one mole of an ionic solid into its gaseous ions. It is influenced by two main factors: the charge of the ions and the size of the ions. Higher charges and smaller ionic radii result in higher lattice energies.
Step 2: Analyzing the Charges of the Ions
In the given compounds:
KCl consists of \( \text{K}^+ \) and \( \text{Cl}^- \) ions.
MgO consists of \( \text{Mg}^{2+} \) and \( \text{O}^{2-} \) ions.
The charges on the ions in MgO are higher (\(2+\) and \(2-\)) compared to those in KCl (\(1+\) and \(1-\)).
Step 3: Considering the Ionic Radii
The ionic radii also play a role in lattice energy. Generally, smaller ions will have a higher lattice energy because they can pack more closely together, increasing the electrostatic attraction.
The ionic radius of \( \text{Mg}^{2+} \) is smaller than that of \( \text{K}^+ \).
The ionic radius of \( \text{O}^{2-} \) is similar to or slightly smaller than that of \( \text{Cl}^- \).
Step 4: Conclusion Based on Lattice Energy Factors
Given that MgO has ions with higher charges and smaller radii compared to KCl, MgO will have a higher lattice energy.
Final Answer
\(\boxed{\text{MgO has the higher lattice energy.}}\)