Question

Is nitric acid the strongest acid and acetic acid the weakest?

Answer 1

According to Lewis theory acid are chemical substances which can accept a pair of electrons whereas according to Bronsted- Lowry theory acid is a chemical substance which can donate protons. Strong acids can completely ionize in dilute aqueous solution to release hydronium ion whereas; weak acids cannot completely ionize in dilute aqueous solution to release hydronium ion and a cation.

Complete answer:
Nitric acid with chemical formula $HN{O_3}$ is one of the strongest acids and a highly corrosive mineral acid which turns blue litmus into red. Whereas, it gets completely dissociated into its ions when dissolved in water thereby releasing ${H^ + }$ ion and nitrate ion. Moreover, the pH of nitric acid is 3. Thus, nitric acid satisfies all the parameters of a strong acid. So, nitric acid can be considered as one of the strongest acids.
Acetic acid with chemical formula $C{H_3}COOH$ is one of the weakest acids as it does not completely dissociate into ${H^ + }$ and $C{H_3}CO{O^ - }$ ion, in dilute aqueous solution. The $p{K_a}$ value of acetic acid is 4.76, moreover greater than the $p{K_a}$ value of an acid, weaker is the acid. Thus, acetic acid is one of the weakest acids.

Note:
The $p{K_a}$ value is inversely proportional to the ka value i.e. greater is the $p{K_a}$ value lower is the ${K_a}$ value and weaker is the acid similarly lower is the $p{K_a}$ value, greater is the ${K_a}$ value and stronger is the acid. Where, ${K_a}$ is the acid dissociation constant and $p{K_a}$ is the negative log of acid dissociation constant.