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Ka × Kb = Kw = 1 × 10^{-14} (at 25°C)
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Ka (acid dissociation constant) and Kb (base dissociation constant) are fundamental constants in acid-base chemistry. For a conjugate acid-base pair, their product equals the water ionization constant Kw at 25°C.
The calculator uses the conjugate acid-base relationship:
Where:
Explanation: This relationship holds true for any conjugate acid-base pair in aqueous solution at 25°C, demonstrating the inverse relationship between acid strength and conjugate base strength.
Details: Understanding the Ka-Kb relationship is crucial for predicting acid-base behavior, calculating pH of solutions, and determining relative strengths of acids and bases in chemical reactions.
Tips: Enter Ka and Kb values in molar units (M). The calculator will compute their product and determine if they form a conjugate acid-base pair by checking if Ka × Kb = 1×10^{-14}.
Q1: What does Ka × Kb = Kw mean?
A: This relationship shows that for any conjugate acid-base pair, the product of their dissociation constants equals the water ionization constant (1×10^{-14} at 25°C).
Q2: Why is Kw = 1×10^{-14}?
A: This value comes from the autoionization of water: H₂O ⇌ H⁺ + OH⁻, where [H⁺][OH⁻] = 1×10^{-14} at 25°C.
Q3: How are Ka and Kb related to pH?
A: Stronger acids have larger Ka values and smaller pKa values, while their conjugate bases have smaller Kb values. The relationship helps predict solution pH.
Q4: Does this relationship hold at different temperatures?
A: No, Kw is temperature-dependent. At different temperatures, Kw changes, so the relationship Ka × Kb = Kw still holds but with a different Kw value.
Q5: What are typical ranges for Ka and Kb values?
A: Ka values range from about 10^{-10} for very weak acids to >10 for strong acids. Kb values follow the inverse relationship through Kw.