Question

The pOH of a sample of baking soda dissolved in water is 5.74 at$25°\text{C}$ . Calculate the pH, $\left[{\text{H}}^{\text{+}}\right]$, and $\left[{\text{OH}}^{-}\right]$for this sample. Is the solution acidic or basic?

Short answer

This is the data received after calculation:

The pH of baking soda solution$=8.26$

The $\left[{\text{OH}}^{-}\right]$ion concentration$=1.82\times {10}^{-6}$

The $\left[{\text{H}}^{\text{+}}\right]$ion concentration$=5.5\times {10}^{-9}$

The solution is basic in nature.

Step-by-step solution

pH and pOH

pH and pOH are related to each other at $25°\text{C}$as

$\text{pH}+\text{pOH}=14$

As given, the pOH of baking soda is5.4.

$\begin{array}{rcl}\text{pH}& =& 14-\text{pOH}\\ & =& 14-5.74\\ & =& 8.26\\ & & \end{array}$

Therefore, the pH of baking sodais $8.26$.

Calculation of  OH- ion Concentration

Here, pOH gives the information about the amount of hydroxyl ion ${\text{OH}}^{-}$present in the solution.

$$\begin{gathered} \text{pOH}=-\log \left[O{H}^{-}\right] \\ 5.74=-\log \left[O{H}^{-}\right] \end{gathered}$$

$\begin{array}{rcl}\left[O{H}^{-}\right]& =& {10}^{-pOH}\\ & =& {10}^{-5.74}\\ & =& 1.82\times {10}^{-6}\\ & & \end{array}$

Therefore, ${\text{OH}}^{-}$ ion concentration in baking soda solution is $1.82\times {10}^{-6}$.

Calculation of H +   ion Concentration

Here, pH gives the information about the amount of hydrogen ion ${\text{H}}^{\text{+}}$present in the solution.

$$\begin{gathered} \text{pH}=-\log \left[H^{+}\right] \\ 8.26=-\log \left[H^{+}\right] \end{gathered}$$

$\begin{array}{rcl}\left[H^{+}\right]& =& {10}^{-pH}\\ & =& {10}^{-8.26}\\ & =& 5.5\times {10}^{-9}\\ & & \end{array}$

So [H⁺] ion concentration in baking soda solution is $5.5\times {10}^{-9}$.

Acidic or Basic

As ${\text{H}}^{\text{+}}$ion concentration $5.5\times {10}^{-9}$in baking soda is lower as compared to $O{H}^{-}$ ion concentration $1.82\times {10}^{-6}$.

Therefore,the solution is basic in nature.