Question

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

Short answer

The pH value of the given buffer solution is 8.49.

Step-by-step solution

Ionic Equilibrium

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

The pH of the buffer solution

Write the 0.95 MHBrOdissociation 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 MKBrOdissociation 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.