Chapter 16.3, Problem 1RC

Interpretation Introduction

Interpretation:

Strongest acid should be identified given the four different molecules.

Concept introduction:

Strong acid: Acid solutions contains hydrigen ions, the higher concentration of hydrogen ions, the lower $pH$ for example hydrochloric acid is strong acid when comapre to acetic acid it is a weakr acid. Hence srong acids are completely ionizaes but weak acids are only partly ionizaed in the solution.

pKa: It is introduced as an index to express the acidity of weak acids, where $p{K}_{\text{a}}$ is defined as fallows, we consider the $K_{\text{a}}$ constant for acetic acid $1.8\times {10}^{-5}(pKa)$ but $p{K}_{\text{a}}$ constant for is 4.8 which is a simpler expression. Furthermore the smaller pKa value has strongest acid.

An acid-base reaction reaction is represented as written below.

$\begin{array}{l}\text{HA}\left(\text{aq}\right)+\text{B}\left(\text{aq}\right)\rightleftharpoons {\text{ BH}}^{\text{+}}\left(\text{aq}\right)+{\text{ A}}^{-}\left(\text{aq}\right)\\ \left(\text{acid}\right)\left(\text{base}\right)\left(\begin{array}{l}\text{conjugate }\\ \text{ acid}\end{array}\right)\left(\begin{array}{l}\text{conjugate }\\ \text{ base}\end{array}\right)\end{array}$

The base will take up the proton from acid and form its conjugate acid and simultaneously acid will form its conjugate base. The equilibrium will be forward or backward can be determined by using the dissociation constants $\left(K_{\text{a}}\text{and }{K}_{\text{b}}\right)$ for reactants as well as of the products. The more the value of $K_{\text{a}}$ for an acid, stronger will be the acid and it will undergo faster ionization. Similarly, higher the value of $K_{\text{b}}$ for a base, stronger will be the base and it will undergo faster ionization.