Chapter 15, Problem 15.102QE

(a)

Interpretation Introduction

Interpretation:

The stronger acid out of ${\text{H}}_{\text{3}}{\text{AsO}}_{\text{3}}$ and ${\text{H}}_3{\text{AsO}}_4$ has to be identified and the reason behind the choice has to be given.

Concept Introduction:

The most common representation of oxy acid is given by ${\left(\text{OH}\right)}_m{\text{XO}}_n$. Here, the subscript $n$ holds importance because the strength of any oxyacid is dependent upon the value of non-hydrogen bonded $\text{O}$ atoms. Oxygen is highly electronegative and hence the electron density in the $\text{O}-\text{H}$ bond gets concentrated in the vicinity of $\text{O}$. This makes $\text{O}-\text{H}$ weaker in strength and hence the proton can be readily lost in an acid-base reaction. More stable is the anion formed after the deprotonation from an acid, higher is the acidic strength.

(b)

Interpretation Introduction

Interpretation:

The stronger acid out of ${\text{PH}}_3$ and ${\text{H}}_{\text{2}}\text{S}$ has to be identified and the reason behind the choice has to be given.

Concept Introduction:

The acidic strength is determined by the ease with the acid that can donate a proton in an aqueous solution. This is determined on the basis of electronegativity of the atoms. Higher the electronegativity more is the electron pair shifted in the vicinity of the electronegative atom, thus more readily the proton can be lost.