Question

The pH of 1.5M solution of HOCl $ {{K}_{a}}=9.6\times {{10}^{-6}}$ is:
(A) 4.42
(B) 2.92
(C) 3.42
(D) None of these

Answer 1

Hint: Before solving this question, first we have to understand what is pH. pH stands for power of hydrogen and it is written as small “p” followed by a capital “H”.

Complete answer:
- pH is the scale which is used to specify the acidity and basicity of a solution. The acidic solutions generally have lower pH value while the basic solutions have higher pH value of the pH scale.
- The formula for calculation if pH is =
\[pH=-\log [{{H}^{+}}]\]
- Similarly, for a base we can calculate the concentration of OH ions using molarity and the calculate pH using the value of pOH.
we know for a acidic solution:
\[\begin{align}
& [{{H}^{+}}]=\sqrt{{{K}_{a}}C} \\
& =\sqrt{9.6\times {{10}^{-6}}\times 0.15} \\
& =\sqrt{1.44\times {{10}^{-6}}} \\
& =0.0012M \\
\end{align}\]
\[pH=-\log [{{H}^{+}}]=-\log [0.0012]=2.920818\]
Hence, the correct answer is option (B) i.e. The pH of 1.5M solution of HOCl is 2.92.

Additional information: Molar solution is also known as molarity. Molarity is one of the standard expressions of solution concentration. The molar solution used the gram molecular weight of a solute in calculating molar concentration present in per litre of the solution. Molarity is denoted by the symbol M. The formula of molarity is given below:

molarity = $ \dfrac{\text{moles of solute}}{liters\text{ of solution}}$

Note: The pH scale generally ranges from 0 to 14. It helps us to determine how acidic or basic the solution is. If the pH of the solution is less than 7, then it is acidic and if the pH of the solution is more than 7, then it is the basic solution.