Chapter 16, Problem 68AP

Interpretation Introduction

Interpretation:

Among the given conditions, the condition which represents a basic solution should be identified.

$\text{pOH}$ = 12.53

$\text{pH}=3.64$

${\text{pOH<[H}}^{+}]$

${\text{[OH}}^{-}]>1.0\times {10}^{-7}\text{ M}$.

Concept Introduction:

Water is an amphoteric in nature implies it can act as an acid as well as base.

Ionization of water is given as:

${\text{H}}_{\text{2}}\text{O}(l)+{\text{H}}_{\text{2}}\text{O}(l)\stackrel{}{\underset{\leftharpoondown }{\rightharpoonup }}{\text{H}}^{\text{+}}(aq)+{\text{OH}}^{-}(aq)$

Here, one water molecule is act as an acid by accepting proton and another molecule of water act as a base by donating proton.

At $25°\text{C}$, the actual concentrations of the products are:

${\text{[H}}^{+}{\text{][OH}}^{-}\text{]=1}\times {\text{10}}^{-14}$

To express the small number, p scale is used, which implies to take the log of a number. Since, the concentration of ${\text{[H}}^{+}\text{]}$ in aqueous solution is small, by using the p scale in the form of $\text{pH}$ scale, it is better way to represent acidity of solution.

Thus, $\text{pH}$ = ${\text{-log [H}}^{+}\text{]}$

Similarly, the relation between $\text{pOH}$ and ${\text{[OH}}^{-}\text{]}$ is given by:

${\text{pOH=-log [OH}}^{-}\text{]}$

The solution is basic when its pH is equal to greater than 7.