1. What is the Kapustinskii Equation?

Definition: The Kapustinskii equation calculates the lattice energy of ionic crystals based on the charges and radii of the constituent ions.

Purpose: It provides a simple method to estimate lattice energy without detailed knowledge of the crystal structure.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( U \) — Lattice energy (J/mol)
• \( N \) — Number of ions in formula unit
• \( z^+ \) — Charge of cation
• \( z^- \) — Charge of anion
• \( r_c \) — Radius of cation (in meters)
• \( r_a \) — Radius of anion (in meters)
• \( [Kapustinskii\_C] \) — Kapustinskii constant (1.20200×10⁻⁴)

3. Importance of Lattice Energy Calculation

Details: Lattice energy helps predict solubility, stability, and melting points of ionic compounds. It's crucial in materials science and chemistry.

4. Using the Calculator

Tips:

• Enter the number of ions in the formula unit
• Provide the charges of cation and anion (absolute values)
• Enter ionic radii in Ångströms (Å)
• All values must be positive numbers

5. Frequently Asked Questions (FAQ)

Q1: What is the Kapustinskii constant?
A: It's an empirical constant (1.20200×10⁻⁴) that makes the equation dimensionally correct and accounts for unit conversions.

Q2: Why use the Kapustinskii equation instead of Born-Landé?
A: Kapustinskii's equation doesn't require knowledge of the crystal structure (Madelung constant), making it simpler for quick estimates.

Q3: How accurate is this calculation?
A: It provides reasonable estimates (within 5% typically) for simple ionic compounds but may be less accurate for complex structures.

Q4: What units should I use for ionic radii?
A: The calculator expects Ångströms (Å) but converts them to meters internally for the calculation.

Q5: Can I use this for polyatomic ions?
A: Yes, but you'll need to use effective ionic radii for polyatomic ions.