How to Calculate Keq From Pka

Equilibrium Constant Formula:

\[ K_{eq} = 10^{-pKa} \]

Equilibrium Constant (Keq):

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1. What is the Keq From Pka Calculation?

The Keq from pKa calculation determines the equilibrium constant for an acid dissociation reaction using the acid dissociation constant (pKa). This relationship is fundamental in chemistry for understanding acid-base equilibria and reaction thermodynamics.

2. How Does the Calculator Work?

The calculator uses the equilibrium constant formula:

\[ K_{eq} = 10^{-pKa} \]

Where:

\( K_{eq} \) — Equilibrium constant (dimensionless)
\( pKa \) — Acid dissociation constant (dimensionless)

Explanation: The pKa value represents the negative logarithm of the acid dissociation constant, so taking the antilogarithm (10^-pKa) gives the actual equilibrium constant value.

3. Importance of Equilibrium Constant Calculation

Details: Calculating Keq from pKa is essential for predicting the extent of acid dissociation, determining reaction spontaneity, and understanding chemical equilibrium positions in various chemical and biological systems.

4. Using the Calculator

Tips: Enter the pKa value as a dimensionless number. The calculator will compute the corresponding equilibrium constant. Typical pKa values range from -10 for strong acids to 50 for very weak acids.

5. Frequently Asked Questions (FAQ)

Q1: What is the relationship between pKa and Keq?
A: pKa is defined as -log₁₀(Ka), where Ka is the acid dissociation constant, so Keq = 10^(-pKa) gives the numerical value of the equilibrium constant.

Q2: What do different pKa values indicate?
A: Lower pKa values indicate stronger acids (higher Ka), while higher pKa values indicate weaker acids (lower Ka).

Q3: Can this calculation be used for bases?
A: For conjugate acid-base pairs, pKa + pKb = 14 (in water at 25°C), so you can calculate base equilibrium constants using this relationship.

Q4: What are typical pKa ranges?
A: Strong acids: pKa < 0, weak acids: pKa 0-10, very weak acids: pKa > 10.

Q5: How accurate is this calculation?
A: The mathematical relationship is exact, but the accuracy depends on the precision of the input pKa value and experimental conditions.