Question

when do we have pka=ph

Answer 1

[AI-generated answer — Explain Bot]

The pKa is the negative logarithm of the acid dissociation constant (Ka) of a compound, indicating its acidity or basicity. The pH, on the other hand, is a measure of the acidity or basicity of a solution.

When the pH of a solution is equal to the pKa of an acidic compound, it indicates that half of the acid molecules have dissociated into their conjugate base form. This is known as the Henderson-Hasselbalch equation:

pH = pKa + log([A-]/[HA])

In the equation, [A-] represents the concentration of the conjugate base (deprotonated form), and [HA] represents the concentration of the acid (protonated form).

To determine when pH = pKa, use the Henderson-Hasselbalch equation. First, rearrange the equation to solve for pH:

pH = pKa + log([A-]/[HA])

Since we want pH = pKa:

pKa = pKa + log([A-]/[HA])

Now, simplify the equation:

log([A-]/[HA]) = 0

Since the logarithm of 1 is 0, it means that [A-] is equal to [HA]. In other words, when the concentration of the conjugate base is the same as the concentration of the acid, the pH of the solution is equal to the pKa of the acid.

So, to have pKa = pH, the concentration of the conjugate base and the concentration of the acid must be equal in the solution.