Question

What is the weakest acid?

Answer 1

Hint:Acid is defined as any substance that contains hydrogen and has the ability to donate protons to another substance. They are usually sour in taste and turn blue litmus to red. Most commonly known acids are hydrochloric acids, sulphuric acids, nitric acids and so on.

Complete step-by-step answer:Acids are divided into two types-
Strong acids- strong acids are defined as any substance that can completely ionise in the aqueous solution. A strong acid dissociates to give hydrogen ions and conjugate base. The conjugate base is very weak. The chloride ion is not capable enough to accept hydrogen ions and become hydrochloric acid again. For example hydrogen chloride completely ionizes into hydrogen ions and chloride ions in the water.
Let us see the ionisation-
$HC{{l}_{(g)}}\to H_{\left( aq \right)}^{+}+Cl_{\left( aq \right)}^{-}$ \[\]
Weak acids- weak acids are defined as any substance that can not completely ionise in the aqueous solution. The weaker acids have a strong conjugate base. For example acetic acid.
Let us see the ionisation-
$C{{H}_{3}}COOH\rightleftarrows H_{\left( aq \right)}^{+}+C{{H}_{3}}COO_{\left( aq \right)}^{-}$
Hydrocyanic acid is the weakest acid with the $p{{K}_{a}}$ value of $9.2$ . It partially ionises in water to give hydrogen ion and cyanide ions. The cyanide ion is the strongest conjugate base. The hydrocyanic acid is then represented as $HCN$ . We can determine weak acid by using Ph. If the value of the Ph is in between $5-6$ , it is said to be a weak acid.

Note:In this question, we have concluded that the weak acid is a substance that does not dissociate completely in water and they have a strong conjugate base. It is to note that pH scale is used to determine how alkaline and acidic a solution is. If Ph ranges from zero to six, it is acidic and if Ph ranges from eight to fourteen, it is basic.