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Acid Dissociation Constant (Ka) Equation:
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The acid dissociation constant (Ka) is a quantitative measure of the strength of an acid in solution. It represents the equilibrium constant for the dissociation reaction of an acid and indicates how completely an acid donates protons in aqueous solution.
The calculator uses the Ka equation:
Where:
Explanation: The equation calculates the acid dissociation constant by relating the concentrations of hydrogen ions, conjugate base, and undissociated acid at equilibrium.
Details: Ka values are crucial for understanding acid strength, predicting acid-base behavior, calculating pH of solutions, and designing buffer systems in chemistry and biochemistry.
Tips: Enter pH value (0-14), conjugate base concentration in molarity (M), and weak acid concentration in molarity (M). All values must be valid and non-negative.
Q1: What is the relationship between Ka and pKa?
A: pKa is the negative logarithm of Ka (pKa = -log₁₀Ka). Lower pKa values indicate 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 Ka ≈ 1.8×10⁻⁵, hydrochloric acid Ka ≈ 10⁷.
Q3: When is this calculation most accurate?
A: This calculation is most accurate for weak acids where the approximation [H⁺] = [A⁻] is valid and for dilute solutions.
Q4: What are the limitations of this calculation?
A: The calculation assumes ideal behavior, neglects activity coefficients, and may not be accurate for concentrated solutions or strong acids.
Q5: How does temperature affect Ka values?
A: Ka values are temperature-dependent. Most acid dissociation constants change with temperature, though the effect is usually small over normal laboratory temperature ranges.