Question

What is the acid ionization constant?
A.Measure of the strength of an acid in solution
B.Number of protons
C.Measure of electrons that dissociate
D.Both A and C

Answer 1

Hint: Acid ionization constant tells us the value or the extent to which an acid dissociates to give the hydrogen ion and the corresponding ion. More is the value of ionization constant, the stronger the acid will be.

Complete Step by step solution:
According to Arrhenius' concept; acids are those which give hydrogen ions and bases are those which give hydroxide ions in the aqueous solution. Bronsted lowry concept describes acid as proton or hydrogen ion donor and base as hydrogen ion or proton acceptor. Lewis concept describes acids as an electron acceptor and base as an electron donor.
Ionization constant or dissociation constant of an acid is a quantitative measure of the strength of the acid in solution. It is the equilibrium constant for the reaction of dissociation of acid into its conjugate base and hydrogen ion. The acid dissociation constant depends on the nature of acid, temperature and initial concentration of acid. Acid dissociation constant of weak acid HA like acetic acid, formic acid can be written as:
\[{\text{HA}} \rightleftharpoons {{\text{H}}^ + } + {{\text{A}}^ - }\]
\[{{\text{K}}_{\text{a}}} = {{\text{K}}_{\text{c}}} = \dfrac{{\left[ {{{\text{H}}^ + }} \right]\left[ {{{\text{A}}^ - }} \right]}}{{\left[ {{\text{HA}}} \right]}}\]
The stronger the value of \[{{\text{K}}_{\text{a}}}\] ; stronger will be the acid. Strong acids can easily liberate \[{{\text{H}}^ + }\] ion. The weaker acid has a low value of \[{{\text{K}}_{\text{a}}}\] .
Similarly ionization constant or dissociation constant of a base is a quantitative measure of the strength of the base in solution. Base dissociation constant of weak base MOH like \[{\text{N}}{{\text{H}}_4}{\text{OH}}\] can be written as:
\[{\text{MOH}} \rightleftharpoons {{\text{M}}^ + } + {\text{O}}{{\text{H}}^ - }\]
\[{{\text{K}}_{\text{b}}} = \dfrac{{\left[ {{{\text{M}}^ + }} \right]\left[ {{\text{O}}{{\text{H}}^ - }} \right]}}{{\left[ {{\text{MOH}}} \right]}}\]
The stronger the value of \[{{\text{K}}_{\text{b}}}\] ; stronger will be the base. Strong base can easily liberate \[{\text{O}}{{\text{H}}^ - }\] . The weak base has a low value of \[{{\text{K}}_{\text{b}}}\] .

Thus, the correct option is A.

Note: Ionization constant or dissociation constant is generally defined for weak acids and weak base as these do not completely dissociate into aqueous solution. Strong acids and bases dissociate completely into hydrogen or hydroxide ions along with conjugate bases and acids.