Question

The pH and pOH of 0.1M aqueous solution of $HN{{O}_{3}}$ are:
(A) 0, 14
(B) 14, 0
(C) 13, 1
(D) 1, 13

Answer 1

Recollect the concept of pH and its normal range. Identify whether the molecule given in the question is acid or base. Start by calculating the pH value of the given compound using the given concentration and calculate the pOH value using the relation, $pH+pOH=14$.

Complete step by step solution:
pH is a scale which is used to specify the acidity or basicity of an aqueous solution. If we get lower pH values of a solution, it means that the solution is more acidic and we know that the solution in which we get higher pH value will be more basic or alkaline in nature. pH values normally range from 1 to 14.
We know that pH scale is logarithmic and inversely indicates the concentration of hydrogen ions in the solution. A lower pH indicates a higher concentration of hydrogen ions. pOH refers to the concentration of hydroxide ions, $O{{H}^{-}}$. pOH values are derived from pH measurements.
$pH+pOH=14$
So, now we know that pOH =14 − pH.
Now, we will calculate pH of nitric acid of 0.1 M concentration.
$pH=-log\left[ {{H}^{+}} \right]$
So, concentration of hydrogen ions in $HN{{O}_{3}}$ is 0.1 M.

& pH=-log\left( 0.1 \right) \\\ & pH=-\log \left( \frac{1}{10} \right) \\\ & pH=-\log {{\left( 10 \right)}^{-1}} \\\ & pH=-1\times -\log (10) \\\ & pH\,of\,HN{{O}_{3}}=1 \\\ \end{aligned}$$ And now by using this formula we will find pOH. $pOH=14-pH$ $pOH=14-1$ pOH of nitric acid=13 So, from this we can say that pH of $HN{{O}_{3}}$ is 1 and pOH of $HN{{O}_{3}}$ is 13. **So, we can say that option D is correct.** **Note:** We use indicators to measure pH. We use the fact that indicators of colour changes with pH. We use a visual comparison of the colour of a test solution with a standard colour chart provides a means to measure pH accurate to the nearest whole number. And that nearest whole number is our measured pH.