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Definition: pKb is the negative base-10 logarithm of the base dissociation constant (Kb) of a weak base.
Purpose: It provides a convenient way to express the strength of weak bases on a logarithmic scale, similar to how pH works for acidity.
The calculator uses the formula:
Where:
Explanation: The smaller the pKb value, the stronger the base. A change of 1 in pKb represents a 10-fold difference in base strength.
Details: pKb values are crucial in chemistry for predicting base strength, buffer solutions, and reaction equilibria involving weak bases.
Tips: Enter the dissociation constant (Kb) of the weak base. The value must be between 0 and 1 (typically very small numbers like 1×10-5).
Q1: What does a high pKb value indicate?
A: A high pKb indicates a weaker base, as it corresponds to a smaller Kb value.
Q2: How is pKb related to pKa?
A: For any conjugate acid-base pair: pKa + pKb = 14 (at 25°C in water).
Q3: What's a typical pKb range for weak bases?
A: Most weak bases have pKb values between 2 and 12 in aqueous solutions.
Q4: Why use logarithmic scale for Kb?
A: The logarithmic scale compresses the wide range of Kb values (often spanning 10 orders of magnitude) into more manageable numbers.
Q5: Can pKb be negative?
A: Yes, if Kb > 1, which would indicate a very strong base (though such bases are rare in aqueous solutions).