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Ka Calculation Formula:
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Ka (acid dissociation constant) is a quantitative measure of the strength of an acid in solution. It represents the equilibrium constant for the dissociation reaction of an acid. The pKa is the negative logarithm of Ka, and Ka can be calculated from pKa using the inverse relationship.
The calculator uses the fundamental relationship:
Where:
Explanation: This mathematical relationship allows conversion between the logarithmic pKa scale and the direct concentration-based Ka value, providing insight into acid strength.
Details: Calculating Ka from pKa is essential for understanding acid-base chemistry, predicting reaction outcomes, determining buffer capacities, and designing chemical processes in various fields including biochemistry, pharmaceuticals, and industrial chemistry.
Tips: Enter the pKa value (can be positive or negative). The calculator will compute the corresponding Ka value in molar concentration (M). Smaller Ka values indicate weaker acids, while larger values indicate stronger acids.
Q1: What is the relationship between Ka and pKa?
A: pKa is the negative base-10 logarithm of Ka: pKa = -log₁₀(Ka). Therefore, Ka = 10^(-pKa).
Q2: What are typical Ka values for common acids?
A: Strong acids have Ka > 1, weak acids have Ka < 1. For example, acetic acid has Ka ≈ 1.8×10⁻⁵, while hydrochloric acid has Ka ≈ 10⁷.
Q3: Why use pKa instead of Ka?
A: pKa provides a more convenient scale for comparing acid strengths, especially for weak acids where Ka values can vary over many orders of magnitude.
Q4: Can Ka be greater than 1?
A: Yes, for strong acids Ka can be much greater than 1, indicating nearly complete dissociation in water.
Q5: How does temperature affect Ka values?
A: Ka values are temperature-dependent. Most dissociation constants are reported at 25°C, and values may change significantly at other temperatures.