Question

Calculate the ratio of imidazole to the imidazolium ion in a solution at pH 7.4.

Answer 1

Concepts and reason

Acid dissociation constant:

Acid dissociation constant of an acid indicates the extent to which the acid dissociates into ion and a conjugate base. Strong acids will have greater dissociation constants, and hence the value will be greater.

Power of hydrogen ions (pH):

The pH of a solution is defined as the negative logarithmic function of the concentration of hydrogen () ions in an aqueous solution at a particular temperature.

Fundamentals

The Henderson-Hasselbalch equation is shown as follows.

Here,

The power of in a solution is .

The power of acid dissociation constant of a weak acid is .

The concentration of a weak monoprotic acid is .

The concentration of its conjugate base is .

The given of the solution is .

The acid dissociation reaction of imidazolium ion is given below.

Use the Henderson-Hasselbalch equation to calculate the ratio as follows.

Substitute for and for

So, the ratio of imidazole to the imidazolium ion is .

Ans:

The ratio of imidazole to the imidazolium ion in a solution at of is .