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Ka Calculation Formula:
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The acid dissociation constant (Ka) measures the strength of an acid in solution. When calculated from percent dissociation, it provides insight into how completely an acid dissociates into its ions in aqueous solution, indicating its relative strength.
The calculator uses the Ka calculation formula:
Where:
Explanation: This formula derives from the equilibrium expression for weak acid dissociation, where α represents the fraction of acid molecules that dissociate into ions.
Details: Calculating Ka from percent dissociation is crucial for understanding acid strength, predicting pH of solutions, designing buffer systems, and studying chemical equilibria in various applications from industrial processes to biological systems.
Tips: Enter initial concentration in molarity (M) and degree of dissociation as a decimal (e.g., 0.05 for 5%). Ensure concentration is positive and dissociation is between 0 and 1 (0% to 100%).
Q1: What does a higher Ka value indicate?
A: A higher Ka value indicates a stronger acid, meaning it dissociates more completely in aqueous solution.
Q2: How is percent dissociation related to α?
A: Percent dissociation = α × 100%. For example, α = 0.025 corresponds to 2.5% dissociation.
Q3: When is this calculation most accurate?
A: This calculation is most accurate for weak acids where α is small (typically less than 5%), as it assumes the approximation 1-α ≈ 1 is valid.
Q4: Can this formula be used for strong acids?
A: No, for strong acids (α ≈ 1), the denominator approaches zero, making the calculation invalid. Strong acids are considered completely dissociated.
Q5: How does concentration affect Ka calculation?
A: Ka is a constant for a given acid at a specific temperature, so it should remain relatively constant regardless of concentration for weak acids.