Question

How do pH and pKa relate?

Answer 1

Hint: pH is the measure of hydrogen ions present in the solution or it tells the acidity or basicity of the solution. The stronger the acid, its pKa will be smaller and the production of the hydrogen ions will be high. The mathematical relation of the pH and pKa can be explained by the Henderson-Hasselbalch equation.

Complete step-by-step answer:A compound will be acidic, basic, or neutral that is indicated by the pH meter. pH is the measure of hydrogen ions present in the solution or it tells the acidity or basicity of the solution. The pH meter is from 0 to 14.
The stronger the acid, its pKa will be smaller and the production or donation of the hydrogen ions will be high.
So, we can say that pH and pKa are directly proportional. The mathematical relation of the pH and pKa can be explained by the Henderson-Hasselbalch equation. But if the compound is highly acidic or highly basic then this equation does not give an approximate value.
The Henderson-Hasselbalch equation is the relation between pH, pKa, conjugate base, and weak acid. The formula is:
$pH=pKa+\log \dfrac{[conjugate\text{ }base]}{[weak\text{ }acid]}$
So, pH is equal to the addition of pKa value and log of the ratio of conjugate base and weak acid.
For acids, both the values of pH and pKa are small.

Note: As we know that pH meter is from 0 to 14, in which 0 – 6.9 tells the acid, 7 is for neutral, and 7.1 to 14 tells the base. For weak acid, the conjugate is when one hydrogen is removed from the acid.