Chapter 16, Problem 67AP

Interpretation Introduction

Interpretation:

Among the given conditions, the condition which represents an acidic solution should be identified.

$\text{pH}$ = 8.95

${\text{[H}}^{+}]<1.0\times {10}^{-7}\text{ M}$

$\text{pOH=3}\text{.46}$

${\text{[OH}}^{-}]=7.11\times {10}^{-10}\text{ M}$.

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 acidic when its pH is equal to less than 7.