Question

How do you calculate the pH of HCl? Explain with example.

Answer 1

pH scale:

• pH scale is a scale that is used to determine the nature of the solution and also for finding the strength of acid and base.
• The pH of a solution can be calculated by using the given formula:

$$\begin{gathered} \mathrm{pH}=-\log \left[{\mathrm{H}}^{+}\right] \\ \mathrm{where}\left[{\mathrm{H}}^{+}\right]=\mathrm{Concentration}\mathrm{of}{\mathrm{H}}^{+}\mathrm{ions} \end{gathered}$$

pH of Hydrochloric acid$\left(\mathrm{HCl}\right)$:

• Hydrochloric acid is a strong acid that completely dissociates into its ions to produce hydrogen ions in aqueous solution.
• The dissociation of hydrochloric acid can be represented as:

$\underset{\mathrm{Hydrochloric}\mathrm{acid}}{\mathrm{HCl}\left(\mathrm{aq}\right)}\to \underset{\mathrm{Hydrogen}\mathrm{ion}}{{\mathrm{H}}^{+}\left(\mathrm{aq}\right)}+\underset{\mathrm{Chloride}\mathrm{ion}}{{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)}$

• Let us consider the molarity of the solution to be $0.1\mathrm{M}$
• Therefore, pH of the solution containing Hydrochloric acid is:

$$\begin{gathered} \mathrm{pH}=-\log \left[{\mathrm{H}}^{+}\right] \\ \mathrm{pH}=-\log [0.1] \\ \mathrm{pH}=-\log [1\times {10}^{-1}] \\ \mathrm{pH}=-\log \left[{10}^{-1}\right] \\ \mathrm{pH}=-(-1)\log \left(10\right) \\ \mathrm{pH}=1[\because \log 10=1] \end{gathered}$$

Therefore, in this manner, we can determine the pH of the Hydrochloric acid solution.