Question

What is the pH value of the solution obtained by mixing equal volumes of 3 solutions with pH 2,4,6.

Answer 1

To answer this question, we first need to understand what is pH. The pH of aqueous or other liquid solutions is a quantitative measure of their acidity or basicity. The phrase, which is frequently used in chemistry, biology, and agronomy, converts hydrogen ion concentrations, which typically vary from around $1 \to {10^{ - 14}}$ gram-equivalents per liter, into numbers between 0 and 14.

Complete answer: Formula to find pH
$pH = - \log [{H^ + }]$
As we are given with the three solutions of equal volume with pH value of 2, 4 and 6.
By putting the value of pH=2.
$2 = - \log [{H^ + }]$
$[{H^ + }] = {10^{ - 2}}$.
Similarly, by putting the value of pH as 4 and 6.
We get the value of $[{H^ + }]$ as ${10^{ - 4}},{10^{ - 6}}$ respectively.
So average amount of $[{H^ + }]$are
$[{H^ + }] = \dfrac{{\left( {{{10}^{ - 2}} + {{10}^{ - 4}} + {{10}^{ - 6}}} \right)}}{3}$
By solving this equation, we get
$[{H^ + }] = 3.367 \times {10^{ - 3}}$.
Here by again using the formula of pH as discussed above
$pH = - \log [{H^ + }]$
$pH = \log [3.367 \times {10^{ - 3}}]$
$pH = 2.4727$
So, the final value of pH is 2.4727.

Note:
A pH meter is used to determine the difference in electromotive force (electrical potential or voltage) between suitable electrodes put in the solution to be tested, which is translated into pH measurements. A pH meter is made up of a voltmeter connected to a pH-responsive electrode and a reference (constant) electrode. The pH-responsive electrode is normally made of glass, and the reference electrode is normally made of mercury-mercurous chloride (calomel), however a silver-silver chloride electrode is also used occasionally.