Concentration of Acid
- We have learned that the acidity of a solution is owing to the presence of hydrogen ions in a solution.
- We need to distinguish between the concentration of acid and the concentration of hydrogen ions of an acid.
- In most cases, the concentration of hydrogen ions has greater significant than the concentration of the acid.
- The concentration of hydrogen ion in acid depends on the
- molarity (concentration) of the acid
The higher the molarity of an acid, the higher the concentration (or molarity) of the hydrogen ions in the acid - strength of the acid
Strong acid has higher concentration of hydrogen ions compare with weak acid of same concentration and same basicity - basicity of the acid
The concentration of hydrogen ions of a diprotic acid is higher than the monoprotic acid and lower than the triprotic acid
Example:
Calculate the number of mol of hydrogen ions that contain in 200cm3 of sulphuric acid 0.4 mol dm-3.
Answer:
Number of mole of sulphuric acid
\[\begin{gathered}
n = \frac{{MV}}{{1000}} \hfill \\
n = \frac{{(0.4)(200)}}{{1000}} \hfill \\
n = 0.08mol \hfill \\
\end{gathered} \]
Sulphuric acid is a diprotic acid. Each molecule of sulphuric acid will produce 2 hydrogen ions when dissolve in water.
Number of mole of hydrogen ions
= 2 x Number of mole of sulphuric acid
= 2 x 0.08 = 0.16 mol