Chapter 12, Problem 12.71P

Write a balanced equation for the incomplete combustion of each alkane: (a) ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}$ ; (b) ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}$ .

Interpretation Introduction

(a)

Interpretation:

The balance equation for the incomplete combustion of ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}$ should 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.

Saturated hydrocarbon is known as alkane having general molecular formula ${\text{C}}_n{\text{H}}_{2n+2}$.

The chemical reaction which involves the reaction of alkane and oxygen, results in the formation of carbon dioxide gas and water vapor is known as combustion reaction. The combustion reaction is an exothermic reaction.

When oxygen is present in limited amount then the combustion is known as incomplete combustion and obtained products during incomplete combustion are carbon monoxide gas and water vapor.

The general reaction of incomplete combustion of alkane is:

  ${\text{C}}_n{\text{H}}_{2n+2}+\frac{(2n+1)}{2}{\text{O}}_{\text{2}}(g)\to n\text{CO}(g)+(n+1){\text{H}}_{\text{2}}\text{O}(g)$

A reaction is said to be balanced, if the number of atoms of each element on the product side and one the reactant side of a chemical reaction are equal.

Answer to Problem 12.71P

  ${\text{2CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}(g)+7{\text{O}}_{\text{2}}(g)\to 6\text{CO}(g)+8{\text{H}}_{\text{2}}\text{O}(g)$

Explanation of Solution

Saturated hydrocarbon in which carbon-carbon single bond is present is known as alkane.

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

The given alkane is ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}$ (propane).

Propane reacts with oxygen (limited) and results in the formation of carbon monoxide gas and water vapor.

The combustion reaction of propane is written as:

  ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}(g)+{\text{O}}_{\text{2}}(g)\to \text{CO}(g)+{\text{H}}_{\text{2}}\text{O}(g)$

Reactant side Product side

Number of C atoms = 3 Number of C atoms = 1

Number of H atoms = 8 Number of H atoms = 2

Number of O atoms = 2 Number of O atoms = 2

Thus, the above reaction is not balanced. To balance the reaction, multiply 2 with propane, 7 with oxygen gas, 6 with carbon monoxide gas and 8 with water vapor.

Therefore, the balanced combustion reaction of propane is written as:

  ${\text{2CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}(g)+7{\text{O}}_{\text{2}}(g)\to 6\text{CO}(g)+8{\text{H}}_{\text{2}}\text{O}(g)$

Interpretation Introduction

(b)

Interpretation:

The balance equation for the incomplete combustion of ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}$ should 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.

Saturated hydrocarbon is known as alkane having general molecular formula ${\text{C}}_n{\text{H}}_{2n+2}$.

The chemical reaction which involves the reaction of alkane and oxygen, results in the formation of carbon dioxide gas and water vapor is known as combustion reaction. The combustion reaction is an exothermic reaction.

When oxygen is present in limited amount then the combustion is known as incomplete combustion and obtained products during incomplete combustion are carbon monoxide gas and water vapor.

The general reaction of incomplete combustion of alkane is:

  ${\text{C}}_n{\text{H}}_{2n+2}+\frac{(2n+1)}{2}{\text{O}}_{\text{2}}(g)\to n\text{CO}(g)+(n+1){\text{H}}_{\text{2}}\text{O}(g)$

A reaction is said to be balanced, if the number of atoms of each element on the product side and one the reactant side of a chemical reaction are equal.

Answer to Problem 12.71P

  ${\text{2CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}(g)+7{\text{O}}_{\text{2}}(g)\to 6\text{CO}(g)+8{\text{H}}_{\text{2}}\text{O}(g)$

Explanation of Solution

Saturated hydrocarbon in which carbon-carbon single bond is present is known as alkane.

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

The given alkane is ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}$ (butane).

Butane reacts with oxygen (limited) and results in the formation of carbon monoxide gas and water vapor.

The combustion reaction of butane is written as:

  ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}(g)+{\text{O}}_{\text{2}}(g)\to \text{CO}(g)+{\text{H}}_{\text{2}}\text{O}(g)$

Reactant side Product side

Number of C atoms = 4 Number of C atoms = 1

Number of H atoms = 10 Number of H atoms = 2

Number of O atoms = 2 Number of O atoms = 2

Thus, the above reaction is not balanced. To balance the reaction, multiply 2 with butane,7 with oxygen gas, 6 with carbon monoxide gas and 8 with water vapor.

Therefore, the balanced combustion reaction of butane is written as:

  ${\text{2CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}(g)+7{\text{O}}_{\text{2}}(g)\to 6\text{CO}(g)+8{\text{H}}_{\text{2}}\text{O}(g)$