Chapter 12, Problem 49A

(a)

Interpretation Introduction

Interpretation:

The $\mathrm{H}-\mathrm{O}-\mathrm{H}$ bond angle of given molecule is to be predicted.

Concept introduction:

VSEPR theory helps to draw the molecular shape as:

Total number of valence electron pairs	Number of bond pairs	Number of lone pairs	Geometry and shape
2	2	0	linear
3	3	0	Trigonal planar
	2	1	bent
4	4	0	Tetrahedral
	3	1	Pyramidal
	2	2	Bent

Shape of molecules gives the bond angle.

Answer to Problem 49A

The $\mathrm{H}-\mathrm{O}-\mathrm{H}$ bond angle in ${\mathrm{H}}_2\mathrm{O}$ is approximately $104\text{'}28\text{'}\text{'}$

Explanation of Solution

Lewis structure of ${\mathrm{H}}_2\mathrm{O}$ is:

  

It shows, there are 2 bond pairs and 2 lone pairs around oxygen atom. Therefore, by VSEPR theory its shape is pyramidal and $\mathrm{H}-\mathrm{O}-\mathrm{H}$ bond angle is approximately $104\text{'}28\text{'}\text{'}$

(b)

Interpretation Introduction

Interpretation:

The $\mathrm{H}-\mathrm{N}-\mathrm{H}$ bond angle of given molecule is to be predicted.

Concept introduction:

VSEPR theory helps to draw the molecular shape as:

Total number of valence electron pairs	Number of bond pairs	Number of lone pairs	Geometry and shape
2	2	0	linear
3	3	0	Trigonal planar
	2	1	bent
4	4	0	Tetrahedral
	3	1	Pyramidal
	2	2	Bent

Shape of molecules gives the bond angle.

Answer to Problem 49A

The $\mathrm{H}-\mathrm{N}-\mathrm{H}$ bond angle in $\mathrm{N}{\mathrm{H}}_3$ is approximately $107\text{'}$

Explanation of Solution

Lewis structure of $\mathrm{N}{\mathrm{H}}_3$ is:

  

It shows, there are 3 bond pairs and 1 lone-pair around nitrogen atom. Therefore, by VSEPR theory its shape is pyramidal and bond angle is $107\text{'}$

(c)

Interpretation Introduction

Interpretation:

The $\mathrm{H}-\mathrm{N}-\mathrm{H}$ bond angle of given molecule is to be predicted.

Concept introduction:

VSEPR theory helps to draw the molecular shape as:

Total number of valence electron pairs	Number of bond pairs	Number of lone pairs	Geometry and shape
2	2	0	linear
3	3	0	Trigonal planar
	2	1	bent
4	4	0	Tetrahedral
	3	1	Pyramidal
	2	2	Bent

Shape of molecules gives the bond angle.

Answer to Problem 49A

The $\mathrm{H}-\mathrm{N}-\mathrm{H}$ bond angle in $\mathrm{N}{\mathrm{H}}_4{}^{+}$ is $109\text{'}28\text{'}\text{'}$

Explanation of Solution

Lewis structure of $\mathrm{N}{\mathrm{H}}_4{}^{+}$ is:

  

It shows, there are 4 bond pairs and no lone pairs around nitrogen atom. Therefore, by VSEPR theory its shape is tetrahedral and bond angle is normal tetrahedron angle.

(d)

Interpretation Introduction

Interpretation:

The $\mathrm{H}-\mathrm{N}-\mathrm{H}$ bond angle of given molecule is to be predicted.

Concept introduction:

VSEPR theory helps to draw the molecular shape as:

Total number of valence electron pairs	Number of bond pairs	Number of lone pairs	Geometry and shape
2	2	0	linear
3	3	0	Trigonal planar
	2	1	bent
4	4	0	Tetrahedral
	3	1	Pyramidal
	2	2	Bent

Shape of molecules gives the bond angle.

Answer to Problem 49A

The $\mathrm{H}-\mathrm{C}-\mathrm{H}$ bond angle in $\mathrm{C}{\mathrm{H}}_4$ is $109\text{'}28\text{'}\text{'}$

Explanation of Solution

Lewis structure of $\mathrm{C}{\mathrm{H}}_4$ is:

  

It shows, there are 4 bond pairs and no lone pairs around carbon atom. Therefore, by VSEPR theory its shape is tetrahedral and bond angle is normal tetrahedron angle.