Question

What is the pH of a 0.01 M solution of the strong acid $HNO_3$ in water?

Answer 1

Hint: pH is defined as a measure of the acidity or basicity of aqueous solutions. pH indicates the concentration of hydrogen ions in the aqueous solution. A strong acid is one that dissociates entirely in water. When working with strong acids, bear in mind that they dissociate fully in an aqueous solution, forming hydronium ions, ${{\text{H}}_3}{{\text{O}}^ + }$ and their conjugate base.

Complete step by step answer:
Complete dissociation occurs when any acid molecule ionizes or donates the acidic proton to a water molecule.
This means that a strong monoprotic acid produces hydronium ions in a 1:1 mole ratio, meaning that one mole of acid produces one mole of hydronium ions.
In our case, nitric acid will dissociate to form
\[{\text{HN}}{{\text{O}}_{3\left( {aq} \right)}} + {{\text{H}}_2}{{\text{O}}_{(l)}}\xrightarrow[{}]{}{{\text{H}}_3}{\text{O}}_{(aq)}^ + + {\text{NO}}_{3(aq)}^ - \]
This implies that the concentration of hydronium ions in the solution would be the same as the concentration of nitric acid.
$[{{\text{H}}_3}{{\text{O}}^ + }] = [{\text{HN}}{{\text{O}}_3}] = 0.01{\text{M}}$
The pH of a solution is simply a calculation of the concentration of hydronium ions in it, as you might know.
${\text{pH}} = - \log ([{{\text{H}}_3}{{\text{O}}^ + }])$
The pH of the solution would be
${\text{pH}} = - \log (0.01) = 2$

Note:
A conjugate base contains one less H atom and an extra negative charge. mole ratio is a conversion factor that connects the quantities of two substances in moles in a chemical reaction
In an aqueous solution, strong acid fully dissociates. The concentration of hydronium ions in water is proportional to the overall concentration (ionized and unionized) of the acid added to a solution due to the complete dissociation of strong acids in an aqueous solution.