Chapter 4, Problem 27E

a)

Interpretation Introduction

Interpretation: Conjugate base for each below acid should be determined. Also, rank of conjugate bases from strongest to weakest P.E. should be determined.

  

Concept introduction: According to the Bronsted-Lowry concept, a substance that donates proton is termed as acid while that accepts or gains protons is called a base. Species formed after loss of protons from acids are known as their respective conjugate bases whereas conjugate acid is produced by the addition of protons to base. The strength of conjugate acids and conjugate bases are inversely related to strengths of their respective bases and acids.

According to Lewis's concept, a substance that donates electron pair is termed as a base while that accepts or gains electron pair is called acid. For example, ${\text{BF}}_{\text{3}}$ is an electron-deficient compound and can easily accept electrons so it is Lewis acid. But ${\text{NH}}_{\text{3}}$ has lone pair of electrons that it can donate easily so it acts as Lewis base.

According to the Arrhenius concept, substances that donate hydrogen ions in solutions are known as acids while bases are substances that release hydroxide ions in solutions.

b)

Interpretation Introduction

Interpretation: Type of orbital that has a lone pair of electrons in the below conjugate base should be drawn.

  

Concept introduction: Hybridization is processed to intermix atomic orbitals in order to form new hybrid orbitals. It can be determined by the calculation of the number of hybrid orbitals $\left(\text{X}\right)$ which is formed by atom. The number of hybrid orbitals $\left(\text{X}\right)$ is calculated as follows:

  $\text{X = }\left[\begin{array}{l}\left(\text{number of atoms bonded to the central atom}\right)+\\ \left(\text{number of lone pairs on the central atom}\right)\end{array}\right]$

Type of hybridization that corresponds to the different number of hybrid orbitals is described in the following table:

  $\begin{array}{cc}\begin{array}{l}\text{Number of}\\ \text{hybrid orbitals}\end{array}& \text{Hybridization}\\ 2& sp\\ 3& s{p}^2\\ 4& s{p}^3\\ 5& s{p}^{3}d\\ 6& s{p}^3{d}^2\end{array}$

c)

Interpretation Introduction

Interpretation: Percent $s$ character of each orbital with lone pair in below conjugate bases should be determined.

  

Concept introduction: Hybridization is processed to intermix atomic orbitals in order to form new hybrid orbitals. It can be determined by the calculation of the number of hybrid orbitals $\left(\text{X}\right)$ which is formed by atom. Number of hybrid orbitals $\left(\text{X}\right)$ is calculated as follows:

  $\text{X = }\left[\begin{array}{l}\left(\text{number of atoms bonded to the central atom}\right)+\\ \left(\text{number of lone pairs on the central atom}\right)\end{array}\right]$

Type of hybridization that corresponds to a different number of hybrid orbitals is described in the following table:

  $\begin{array}{cc}\begin{array}{l}\text{Number of}\\ \text{hybrid orbitals}\end{array}& \text{Hybridization}\\ 2& sp\\ 3& s{p}^2\\ 4& s{p}^3\\ 5& s{p}^{3}d\\ 6& s{p}^3{d}^2\end{array}$

d)

Interpretation Introduction

Interpretation: Whether $s$ orbital or $p$ orbital is lower in PE should be determined.

Concept introduction: Orbitals are defined as regions around atomic nucleus where electrons are found. Atomic orbitals help to form covalent bonds. Atomic orbitals can be $s$ , $p$ , $d$ and $f$ orbitals.

e)

Interpretation Introduction

Interpretation: Reason for pattern in $\text{p}{K}_{\text{a}}$ data should be determined.

Concept introduction: $\text{p}{K}_{\text{a}}$ is defined as the negative logarithm of the dissociation constant of acid $\left(K_a\right)$ . If conjugate acid has a high $\text{p}{K}_a$ value, its dissociation constant will be less. As a result, it cannot dissociate completely in solutions and acts as a weak acid. The strength of the base and its conjugate acid are inversely related to each other. So base that corresponds to weak conjugate acid will be a strong base. Higher the $\text{p}{K}_a$ of conjugate acid, the stronger the base and vice-versa.