Question

Acetic acid is a weak acid
A True
B False

Answer 1

Hint: A weak acid is defined as a substance that partially dissociates when dissolved in a solvent and the strength of a weak acid is quantified in terms of dissociation constant Ka.We can also say that a weak acid is that which do not liberate hydrogen ion easily when dissolved in water,

Complete Step by step answer: Acetic acid is also called an Ethanoic acid, It is a colourless liquid organic compound with the chemical formula (). Acetic acid is a weak acid because it partially dissociates into its constituent ions when dissolved in water. This weak acid is known to form miscible mixtures with water. An acetic acid is an acid that ionizes only slightly in an aqueous solution. Acetic acid (found in vinegar) is a very common weak acid. Its ionization is shown below.
\[C{H_3}COOH\left( {aq} \right)\; \rightleftharpoons {H^ + }\left( {aq} \right) + C{H_3}CO{O^ - }\left( {aq} \right)\]
The ionization of acetic acid is incomplete, and so the equation is shown with a double arrow. The extent of ionization of weak acids varies, but is generally less than\[10\% \]. Because the acid is weak, an equilibrium expression can be written. An acid ionization constant\[(Ka\]) is the equilibrium constant for the ionization of an acid.
\[{K_a} = \left[ {{H^ + }} \right]\left[ {{A^ - }} \right]/\left[ {HA} \right]\]
The acid ionization represents the fraction of the original acid that has been ionized in solution. Therefore, the numerical value of Ka is a reflection of the strength of the acid. Weak acids with relatively higher Ka values are stronger than acids with relatively lower Ka values.

Any strong or a good acid will ionize completely in an aqueous solution. Let's take HCl, it will ionize completely in water giving all the H+ it has as follows, In case of acetic acid Comparatively the amount of H+ dissociated is very small. Therefore it's a weak acid.

Hence the correct option is A.

Note: As per Bronsted-Lowry definition of an acid acts as a proton donor. This means that they dissociate to form a negatively charged ion and a proton (which combines with water molecules to form \[{\left( {{H_3}O} \right)^{ + .}}\] Weak acids generally don't ionise fully when they are dissolved in water.