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Ka From pKa Formula:
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The Ka From pKa calculation converts the logarithmic pKa value to the acid dissociation constant (Ka), which quantifies the strength of an acid in solution. pKa is the negative logarithm of Ka, making this conversion essential for acid-base chemistry calculations.
The calculator uses the fundamental relationship:
Where:
Explanation: This mathematical relationship allows conversion between the logarithmic scale (pKa) used for convenience and the actual dissociation constant (Ka) used in equilibrium calculations.
Details: Knowing the exact Ka value is crucial for predicting acid strength, calculating pH of solutions, determining buffer capacities, and understanding chemical equilibrium in acid-base reactions.
Tips: Enter the pKa value as a dimensionless number. The calculator will compute the corresponding Ka value in molar concentration (M). Higher Ka values indicate stronger acids.
Q1: What is the relationship between Ka and pKa?
A: pKa = -log₁₀(Ka), so Ka = 10^(-pKa). They are inversely related - lower pKa values correspond to higher Ka values and stronger acids.
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 (pKa = 4.76), while hydrochloric acid has Ka ≈ 10⁷ (pKa = -7).
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 span many orders of magnitude.
Q4: How precise should my pKa input be?
A: For most applications, 2-3 decimal places are sufficient. The calculator accepts up to 4 decimal places for high-precision requirements.
Q5: Can this calculator handle negative pKa values?
A: Yes, negative pKa values indicate very strong acids with Ka > 1. The calculator properly handles all real number inputs.