Q19.16P - Chemistry: Molecular Nature Of Matter And Change

Question

Find the pH of a buffer that consists of 0.95 M HBrO and 0.68 M KBrO ( ${\mathbf{\text{pK}}}_{\mathbf{\text{a}}}$of HBrO=8.64).

Step-by-Step Solution

Answer

The pH value of the given buffer solution is 8.49.

Step 1: Ionic Equilibrium

An ionic equilibrium refers to an equilibrium that exists in the solution of weak electrolytes between unionized molecules and ions.

Step 2: The pH of the buffer solution

Write the 0.95 M HBrO dissociation equation first.

${\text{HBrO + H}}_{\text{2}}\text{O}\rightleftharpoons {\text{BrO}}^{\text{ - }}{\text{ + H}}_{\text{3}}{\text{O}}^{\text{ + }}.$

Then, write the 0.68 M KBrO dissociation equation.

$\text{KBrO}\to {\text{BrO}}^{\text{ - }}{\text{ + K}}^{\text{ + }}.$

We now have the initial hypobromus acid and hypobromite concentrations.

$$\begin{gathered} \text{ HBrO = 0.95 M.} \\ {\text{BrO}}^{\text{ - }}\text{ = 0.68 M.} \end{gathered}$$

To find the pH, we may utilize the Henderson-Hasselbalch equation.

$$\begin{gathered} \text{pH = pKa + log}\frac{\left[{\text{BrO}}^{\text{ - }}\right]}{\left[\text{HBrO}\right]} \\ \text{ = 8.64 + log}\frac{\text{0.68 M}}{\text{0.95 M}} \\ \text{ = 8.49.} \end{gathered}$$

Therefore, the pH value of the given buffer solution is 8.49.