Chapter 9, Problem 128A

(a)

Interpretation Introduction

Interpretation: Identify whether the given substance is polar or non-polar.

Concept Introduction: A polar molecule contains positive and negative poles. They occur when covalently bonded atoms do not share electrons equally, leading to the formation of slight charge separation within the molecule.

Answer to Problem 128A

The ${\text{Cl}}_{\text{2}}$ molecule contains two chlorine atoms and hence is non-polar.

Explanation of Solution

  ${\text{Cl}}_{\text{2}}$ contains two chlorine atoms bonded together through a covalent bond. Since both atoms are the same, there is no electronegativity difference. Hence it is non-polar.

(b)

Interpretation Introduction

Interpretation: Identify whether the given substance is polar or non-polar.

Concept Introduction: A polar molecule contains positive and negative poles. They occur when covalently bonded atoms do not share electrons equally, leading to the formation of slight charge separation within the molecule.

Answer to Problem 128A

The carbon monoxide $\left(\text{CO}\right)$ molecule is polar.

Explanation of Solution

Carbon monoxide contains one carbon atom and an oxygen atom. Oxygen is more electronegative than a carbon atom and will attract the bonded pair of electrons toward it. Thus oxygen will attain a partial negative charge and carbon will attain a partial positive charge, forming a polar molecule.

(c)

Interpretation Introduction

Interpretation: Identify whether the given substance is polar or non-polar.

Concept Introduction: A polar molecule contains positive and negative poles. They occur when covalently bonded atoms do not share electrons equally, leading to the formation of slight charge separation within the molecule.

Answer to Problem 128A

Carbon dioxide $\left({\text{CO}}_{\text{2}}\right)$ is a linear non-polar molecule.

Explanation of Solution

  ${\text{CO}}_{\text{2}}$contains two carbon-oxygen bonds that are polar because of the electronegativity difference between C and O. but in the linear ${\text{CO}}_{\text{2}}$molecule, these two polar bonds lie opposite to each other and hence the dipoles cancel each other out.

(d)

Interpretation Introduction

Interpretation: Identify whether the given substance is polar or non-polar.

Concept Introduction: A polar molecule contains positive and negative poles. They occur when covalently bonded atoms do not share electrons equally, leading to the formation of slight charge separation within the molecule.

Answer to Problem 128A

The ammonia molecule $\left({\text{NH}}_{\text{3}}\right)$ is polar.

Explanation of Solution

Due to the electronegativity difference between nitrogen and hydrogen atoms, ${\text{NH}}_{\text{3}}$ contains three polar $\text{N}-\text{H}$ bonds. Due to the pyramidal structure of ammonia, the dipoles do not cancel out. Hence ${\text{NH}}_{\text{3}}$ is polar.

(e)

Interpretation Introduction

Interpretation: Identify whether the given substance is polar or non-polar.

Concept Introduction: A polar molecule contains positive and negative poles. They occur when covalently bonded atoms do not share electrons equally, leading to the formation of slight charge separation within the molecule.

Answer to Problem 128A

Carbon tetrachloride is a non-polar molecule.

Explanation of Solution

  ${\text{CCl}}_{\text{4}}$is a tetrahedral molecule with four polar carbon-chlorine bonds. But due to the symmetry of the tetrahedral structure, the dipoles cancel out each other and the net dipole moment is zero. Hence ${\text{CCl}}_{\text{4}}$is non-polar.

(f)

Interpretation Introduction

Interpretation: Identify whether the given substance is polar or non-polar.

Concept Introduction: A polar molecule contains positive and negative poles. They occur when covalently bonded atoms do not share electrons equally, leading to the formation of slight charge separation within the molecule.

Answer to Problem 128A

Water is a polar bent molecule.

Explanation of Solution

The water molecule contains two polar hydrogen-oxygen bonds. Unlike ${\text{CO}}_{\text{2}}$ , ${\text{H}}_{\text{2}}\text{O}$ have a bent structure, so its dipole does not cancel each other. Thus ${\text{H}}_{\text{2}}\text{O}$ is a polar molecule.

(g)

Interpretation Introduction

Interpretation: Identify whether the given substance is polar or non-polar.

Concept Introduction: A polar molecule contains positive and negative poles. They occur when covalently bonded atoms do not share electrons equally, leading to the formation of slight charge separation within the molecule.

Answer to Problem 128A

Methane is a non-polar tetrahedral molecule with four carbon-hydrogen bonds.

Explanation of Solution

  ${\text{CH}}_{\text{4}}$ contains four C-H bonds, but the electronegativity difference between carbon and hydrogen is very small. Hence there is no partial charge separation and the molecule is non-polar.