Lattice Energy using Kapustinskii equation Calculator

Kapustinskii Equation:

\[ U_{Kapustinskii} = \frac{1.20200 \times 10^{-4} \times N_{ions} \times z^+ \times z^- \times (1 - \frac{3.45 \times 10^{-11}}{R_c + R_a})}{R_c + R_a} \]

Number of Ions:

Charge of Cation (z+):

Charge of Anion (z-):

Radius of Cation:

Radius of Anion:

Lattice Energy:

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1. What is the Kapustinskii Equation?

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

Purpose: It provides a way to estimate lattice energy when more detailed structural information is unavailable.

2. How Does the Calculator Work?

The calculator uses the Kapustinskii equation:

\[ U_{Kapustinskii} = \frac{1.20200 \times 10^{-4} \times N \times z^+ \times z^- \times (1 - \frac{d}{R_c + R_a})}{R_c + R_a} \]

Where:

\( U \) — Lattice energy (kJ/mol)
\( N \) — Number of ions in formula unit
\( z^+ \) — Charge of cation (in elementary charge units)
\( z^- \) — Charge of anion (in elementary charge units)
\( R_c \) — Radius of cation (Å)
\( R_a \) — Radius of anion (Å)
\( d \) — Constant (3.45×10⁻¹¹ m)

3. Importance of Lattice Energy Calculation

Details: Lattice energy helps predict solubility, stability, and melting points of ionic compounds.

4. Using the Calculator

Tips: Enter the number of ions, cation/anion charges (with sign), and their radii in Ångströms (Å). All values must be positive except charges.

5. Frequently Asked Questions (FAQ)

Q1: What units does this calculator use?
A: Radii in Å (1Å = 10⁻¹⁰m), charges in elementary charge units, and results in kJ/mol.

Q2: How accurate is the Kapustinskii equation?
A: It provides reasonable estimates (±5%) for many ionic compounds but may vary for complex structures.

Q3: What's a typical range for lattice energies?
A: Most ionic compounds range from 700-4000 kJ/mol.

Q4: Can I use this for covalent compounds?
A: No, this is specifically for ionic compounds with significant charge separation.

Q5: Why does the equation include (1 - d/(Rc+Ra))?
A: This term accounts for the repulsion between electron clouds at short distances.