Question

What is the pH of the following solutions?
A.${10^{ - 3}}M\,HCL$
B.$0.0001M\,NaOH$
C.$0.0001M\,{H_2}S{O_4}$

Answer 1

Hint: pH ('potential of hydrogen' or 'power of hydrogen') is a chemical scale for determining the acidity or basicity of an aqueous solution. Acidic solutions (those containing a larger concentration of \[{H^ + }\]ions) have a lower pH than basic or alkaline solutions.

Complete answer:
The pH of a chemical solution indicates how acidic or basic it is. A pH value of seven is considered neutral, less than seven acidic, and greater than seven basic on the pH scale, which ranges from \[0\] to\[14\]
Acids and bases are defined in a variety of ways, but pH relates exclusively to hydrogen ion concentration and is used to describe aqueous (water-based) solutions. When water dissociates, a hydrogen ion and a hydroxide are produced.
${H_2}O \leftrightarrow \,{H^ + } + O{H^ - }$
Remember that [ ] stands for molarity, M, when calculating pH. The molarity of a solution is measured in moles of solute per litre of solution. If the concentration is given in a unit other than moles (mass percent, molality, etc. ), convert it to molarity before applying the pH formula.
pH can be calculated as:
\[pH{\text{ }} = {\text{ }} - log{\;_{10}}[H{\;^ + }]\]
\[[H{\;^ + }]{\text{ }} = {\text{ }}10{\;^{ - pH}}\]
Now, lets come to problem
(a)
\[HCl\] is a strong electrolyte that is fully ionised.
$HCl \rightleftharpoons {H^ + } + C{l^ - }$
So, $[{H^ + }] = {10^{ - 3}}\,M$
pH$ = - \log [{H^ + }]\, = - \log \,{10^{ - 3}} = 3$
(b) $NaOH$ is a strong electrolyte that is fully ionized.
$NaOH \rightleftharpoons N{a^ + } + O{H^ - }$
So, $[O{H^ + }] = 0.0001M = {10^{ - 4}}M$
$pOH = - \log \,{10^{ - 4}} = 4$
(c). ${H_2}S{O_4}$ is a strong electrolyte that is fully ionised
${H_2}S{O_4} \rightleftharpoons 2{H^ + } + SO_4^{2 - }$
So, $[{H^ + }] = 2 \times {10^{ - 4}}\,M$
$pH = - \log [{H^ + }] = 3.70$

Note:
A glass electrode with a pH metre, or a color-changing indicator, can be used to determine the pH of aqueous solutions. pH measurements are useful in chemistry, agronomy, medicine, water treatment, and a variety of other fields.