Question

The concentration of $\mathit{O}{\mathit{H}}^{\mathbf{-}}$in a solution of household bleach is$\mathbf{3}\mathbf{.}\mathbf{6}\mathbf{\times }{\mathbf{10}}^{\mathbf{-}\mathbf{2}}\mathit{M}$. Calculate the pH of the bleach.

Short answer

The pH of the bleach is 12.5.

Step-by-step solution

Understanding the concept of pH of an acid-base

The negative logarithm of$H^{+}$ion concentration is used to calculate pH. It's a scale that is used to measure acids and bases.

$\mathit{p}\mathit{H}\mathbf{=}\mathbf{-}\mathit{l}\mathit{o}\mathit{g}\left[H_3{O}^{+}\right]$

Applying the concept and calculation of pH.

By definition, the mathematical expression of pH could be written as:

$pH=-\log \left(O{H}^{-}\right)$

Given concentration of $H_3{O}^{+}$in the sample of wine is $2\times {10}^{-4}M$, and after applying the value in the mathematical expression written above,

$pOH=-\log \left[3.6\times {10}^{-2}M\right]$

Now apply the properties of logarithm,

$$\begin{gathered} \log \left(a\times b\right)=\log a+\log b \\ \log a^x=x\log a \end{gathered}$$

The above expression could be rewritten as:

$$\begin{gathered} pOH=-\log 3.6+\left(-\log {10}^{-2}\right) \\ pOH=1.5 \end{gathered}$$

After using the formula , pH + pOH =14

pH could be written as 14 - 1.5 = 12.5

The value of pH here is more than 7 which means the sample is basic in nature.