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How does pH relate to pKa?

Answer 1

Zoe Alexander

#"pH"# is the negative logarithm of the concentration of protons in solution as a result of dissolving the acid.

#pK_"a"# is the negative logarithm of the equilibrium expression of the acid dissociating.

#HA rightleftharpoons H^(+) + A^(-)#, where

#K_a = ([H^+][A^-])/([HA])#

It is true that each "power" has a low magnitude if its subject is high.

As a result, an extremely acidic substance will have a very high proton concentration and a numerator that is greater than the denominator in the equilibrium expression.

As a result, for a strong acid, both will be low, and for a strong base, both will be high.

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Answer 2

Carter Allen

The pH of a solution is a measure of its acidity or alkalinity, determined by the concentration of hydrogen ions present. The pKa of a compound is the negative logarithm of its acid dissociation constant (Ka), which quantifies the strength of an acid in solution. The relationship between pH and pKa is described by the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]), where [A-] is the concentration of the conjugate base and [HA] is the concentration of the acid. This equation illustrates that when the pH of a solution is equal to the pKa of an acid, the concentrations of the acid and its conjugate base are equal, resulting in a solution that is half dissociated. Additionally, the difference between the pH of a solution and the pKa of an acid can provide insight into the extent of ionization of the acid in solution.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.