Chapter 10.3, Problem 10.10P

Interpretation Introduction

Interpretation:

The stronger conjugate base obtained from given set of acids with $K_a$ values should be identified.

Concept Introduction:

$\text{Bronsted-Lowry Acids}$: If a species loses a proton then it is considered as $\text{Bronsted-Lowry acid}\text{.}$

$\text{Bronsted-Lowry Base}$: If a species receives one proton, then it is considered as $\text{Bronsted-Lowry base}\text{.}$

If a base receives one proton, then the formed species is a conjugate acid whereas an acid lose one proton, then the formed species is a conjugated base.

Stronger the acid weaker it’s conjugate base and vice versa.

The degree to which a weak acid ionizes depends on the concentration of the acid and the equilibrium constant for the ionization.

$K_a$: Acid dissociation constant ${\text{K}}_{\text{a}}$ represents how strong the acid is in a solution.

Equilibrium constant ${\text{K}}_{\text{eq}}$ represents extend of dissociation of acid in aqueous solution.

For a dissociation of acid $\left(HA\right)$ in aqueous solution,

$HA+H_{2}O\underset{}{\overset{}{\rightleftharpoons }}{H}_3{O}^{+}+A^{-}$

$k_{eq}=\frac{\left[H_3{O}^{+}\right]\left[A^{-}\right]}{\left[HA\right]\left[H_{2}O\right]}$

Where,

${\text{K}}_{\text{a}}\to \text{acid ionization constant}$

${\text{[H}}^{\text{+}}\text{]}\to \text{concentration of hydrogen ion}$

${\text{[A}}^{\text{-}}\text{]}\to \text{concentration of acid anion}$

$\text{[HA]}\to \text{concentration of the acid}$

Relationship between ${\text{K}}_{\text{eq}}$ and ${\text{K}}_{\text{a}}$,

${\text{K}}_{\text{a}}\text{=}{\text{K}}_{\text{eq}}\left[{\text{H}}_{\text{2}}\text{O}\right]$

Where,

$\left[{\text{H}}_{\text{2}}\text{O}\right]$ is the molar concentration of water

Generally, strong acids have ${\text{K}}_{\text{a}}>1$ and weak acids have ${\text{K}}_{\text{a}}<1$