Question

The pH of 0.001 M \[C{H_3}COOH\]?
A. 3
B. 11
C. between 3 and 7
D. 7

Answer 1

Hint: The pH of acid measures the acidic strength of acid. The pH is the negative logarithm of hydrogen ion concentration. The acetic acid dissolves in water and partially dissociates into acetate ion and hydrogen ion.

Complete step by step answer:
-The concentration of \[C{H_3}COOH\] is 0.001 M.
-The acetic acid is a weak acid so on dissolving in water it partially dissociates into its constituent ions.
-The dissociation of acetic acid into its constituent ions is shown below.
\[C{H_3}COOH \to C{H_3}CO{O^ - } + {H^ + }\]
-The acetic acid on dissolving in water dissociates into acetate ion and hydrogen ion.
-As one hydrogen ion is present therefore the concentration of hydrogen ion will be 0.001 or \[{10^{ - 3}}\].
-The pH is the measure of the acidic nature and basic nature of the compound. The pH scale ranges from 1 to 14. When the pH of the solution of compound is less than 7 then the compound is acidic in nature. When the pH of the solution of compound is more than 7 then the compound is basic in nature. When the pH of the solution of compound is 7 then the compound is neutral in nature.
-The pH of an acid is defined as the negative logarithm of hydrogen ion concentration.
-The pH of the acid is calculated by the formula as shown below.
\[pH = - \log [{H^ + }]\]
-To calculate the pH, substitute the value in the above equation.
\[ \Rightarrow pH = - \log [{10^{ - 3}}]\]
\[ \Rightarrow pH = 3\]
-Thus, the pH of 0.001 M \[C{H_3}COOH\] is 3.
Therefore, the correct option is A.

Note:
The calculated value is 3 but as the acetic acid is a weak acid, the pH of the acid will change but it will be below 7. Thus the pH will lie between 3 to 7. So, option C can also be correct.