Chapter 20, Problem 1E

Write the chemical formula and Lewis structure of the following each of which contains five carbon atoms:

(a) an alkane.

(b) an alkene.

(c) an alkyne

Interpretation Introduction

Interpretation:

The chemical formula and Lewis structure of an alkane with five carbon atoms are to be written.

Concept Introduction:

Compounds consist of carbon and hydrogen is known as hydrocarbons. Hydrocarbons are classified as saturated hydrocarbon and unsaturated hydrocarbon. Saturated hydrocarbons are those hydrocarbons in which carbon-carbon single bond is present as carbon is linked with four atoms. Unsaturated hydrocarbons are those hydrocarbons in which carbon-carbon multiple bonds are present that is double and triple bond.

The completely saturated hydrocarbon is known as an alkane.

The general molecular formula of alkane is ${\text{C}}_n{\text{H}}_{2n+2}$ where n represents the number of carbon atoms.

Answer to Problem 1E

Chemical formula: ${\text{C}}_{\text{5}}{\text{H}}_{\text{12}}$

Lewis structure:

  

Pentane

Explanation of Solution

The general formula of alkane is ${\text{C}}_{\text{n}}{\text{H}}_{\text{2n+2}}$

In case of five carbon atoms, the molecular formula of alkane is $C_5{H}_{(5\times 2)+2}$ = $C_5{H}_{12}$

• Lewis structures are the diagrams that show the bonding between the atoms of the molecules and existing lone pairs of electrons.
• Bonding electrons are those electrons which are shared between the atoms resulting in the formation of bond.
• Non-bonding electrons are the valence electrons of the atom which are not shared with another atom.

Number of valence electrons in a carbon atom = 4

Number of valence electrons in a hydrogen atom = 1

Total number of valence electrons = $\left(\text{4}\times \text{5}\right)+\left(12\times 1\right)$

             = 32

Thus, Lewis structure of alkane having five carbon atoms is:

   Or,

Interpretation Introduction

Interpretation:

The chemical formula and Lewis structure of an alkene with five carbon atoms are to be written.

Concept Introduction:

Compounds consist of carbon and hydrogen is known as hydrocarbons. Hydrocarbons are classified as saturated hydrocarbon and unsaturated hydrocarbon. Saturated hydrocarbons are those hydrocarbons in which carbon-carbon single bond is present as carbon is linked with four atoms. Unsaturated hydrocarbons are those hydrocarbons in which carbon-carbon multiple bonds are present that is double and triple bond.

The unsaturated hydrocarbon with one or more double bond is known as an alkene.

The general molecular formula of alkene is ${\text{C}}_n{\text{H}}_{2n}$ where n represents the number of carbon atoms.

Answer to Problem 1E

Chemical formula: ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}$

Lewis structure:

  

Explanation of Solution

The general formula of alkene is ${\text{C}}_{\text{n}}{\text{H}}_{\text{2n}}$

In case of five carbon atoms, the molecular formula of alkene is $C_5{H}_{(5\times 2)}$ = $C_5{H}_{10}$

• Lewis structures are the diagrams that show the bonding between the atoms of the molecules and existing lone pairs of electrons.
• Bonding electrons are those electrons which are shared between the atoms resulting in the formation of bond.
• Non-bonding electrons are the valence electrons of the atom which are not shared with another atom.

Number of valence electrons in a carbon atom = 4

Number of valence electrons in a hydrogen atom = 1

Total number of valence electrons = $\left(\text{4}\times \text{5}\right)+\left(10\times 1\right)$

           = 30

Thus, Lewis structure of alkene having five carbon atoms is:

  Or,

Interpretation Introduction

Interpretation:

The chemical formula and Lewis structure of an alkyne with five carbon atoms are to be written.

Concept Introduction:

Compounds consist of carbon and hydrogen is known as hydrocarbons. Hydrocarbons are classified as saturated hydrocarbon and unsaturated hydrocarbon. Saturated hydrocarbons are those hydrocarbons in which carbon-carbon single bond is present as carbon is linked with four atoms.Unsaturated hydrocarbons are those hydrocarbons in which carbon-carbon multiple bonds are present that is double and triple bond.

The unsaturated hydrocarbon with one or more triple bond is known as an alkyne.

The general molecular formula of alkyne is ${\text{C}}_n{\text{H}}_{2n-2}$ where n represents the number of carbon atoms.

Answer to Problem 1E

Chemical formula: ${\text{C}}_{\text{5}}{\text{H}}_{\text{8}}$

Lewis structure:

  

Explanation of Solution

The general formula of alkyne is ${\text{C}}_{\text{n}}{\text{H}}_{\text{2n-2}}$

In case of five carbon atoms, the molecular formula of alkyne is $C_5{H}_{(5\times 2)-2}$ = $C_5{H}_8$

• Lewis structures are the diagrams that show the bonding between the atoms of the molecules and existing lone pairs of electrons.
• Bonding electrons are those electrons which are shared between the atoms resulting in the formation of bond.
• Non-bonding electrons are the valence electrons of the atom which are not shared with another atom.

Number of valence electrons in a carbon atom = 4

Number of valence electrons in a hydrogen atom = 1

Total number of valence electrons = $\left(\text{4}\times \text{5}\right)+\left(8\times 1\right)$

           = 28

Thus, Lewis structure of alkyne having five carbon atoms is:

   Or,