Chapter 3, Problem 3.85QP

Propane (C₃H₈) is a component of natural gas and is used in domestic cooking and heating. (a) Balance the following equation representing the combustion of propane in air.

${\text{C}}_3{\text{H}}_8+{\text{O}}_2\stackrel{}{\to }{\text{CO}}_2+{\text{H}}_2\text{O}$

(b) How many grams of carbon dioxide can be produced by burning 3.65 moles of propane? Assume that oxygen is the excess reactant in this reaction.

Interpretation Introduction

Interpretation:

The given reaction representing combustion of propane in air has to be balanced.

Concept Introduction:

Balanced Chemical equation:

A balanced chemical equation is an equation which contains same elements in same number on both the sides (reactant and product side) of the chemical equation thereby obeying the law of conservation of mass.

Answer to Problem 3.85QP

The balanced equation for the combustion reaction of propane is $C_3{H}_8{}_{(g)}+5O_2{}_{(g)}\stackrel{}{\to }3C{O}_2{}_{(g)}+4H_2{O}_{(l)}$

Explanation of Solution

Given data:

Propane is a component of natural gas and is used in domestic cooking and heating.

The given unbalance equation representing the combustion of propane in air is:

${\text{C}}_{\text{3}}{\text{H}}_{\text{8}}\text{+}5{\text{O}}_{\text{2}}\to 3{\text{CO}}_{\text{2}}\text{+}4{\text{H}}_{\text{2}}\text{O}$

Balancing the given equation:

The given equation is ${\text{C}}_{\text{3}}{\text{H}}_{\text{8}}\text{+}5{\text{O}}_{\text{2}}\to 3{\text{CO}}_{\text{2}}\text{+}4{\text{H}}_{\text{2}}\text{O}$

The above unbalanced equation is balanced by the following steps.

• Carefully go through the given chemical reaction, find compound with greater subscript.
• In our reaction propane has subscript of 3 and 8, then look at where are hydrogen and carbon.
• Give 4, 3 and 5 coefficients for water, carbon dioxide and oxygen which makes the equation balanced.

Hence, the balanced equation is $C_3{H}_8{}_{(g)}+5O_2{}_{(g)}\stackrel{}{\to }3C{O}_2{}_{(g)}+4H_2{O}_{(l)}$

Conclusion

The balanced equation for the combustion reaction of propane was written as $C_3{H}_8{}_{(g)}+5O_2{}_{(g)}\stackrel{}{\to }3C{O}_2{}_{(g)}+4H_2{O}_{(l)}$

Interpretation Introduction

Interpretation:

The amount of ${\text{CO}}_{\text{2}}$ produced by burning $\text{3}\text{.65 moles}$ of propane in the given reaction has to be calculated.

Concept Introduction:

Amount of substance:

$\text{Grams of the substance = moles of the substance }\times \frac{\begin{array}{l}\text{ molar mass of }\\ \text{substance in grams}\end{array}}{\text{ one mole}}$

Figure 1

Answer to Problem 3.85QP

The amount of ${\text{CO}}_{\text{2}}$ produced by burning $\text{3}\text{.65 moles}$ of propane is $481.8gofC{O}_2$

Explanation of Solution

Given data:

Propane is a component of natural gas and is used in domestic cooking and heating.

The given unbalance equation representing the combustion of propane in air is:

${\text{C}}_{\text{3}}{\text{H}}_{\text{8}}\text{+}5{\text{O}}_{\text{2}}\to 3{\text{CO}}_{\text{2}}\text{+}4{\text{H}}_{\text{2}}\text{O}$

Amount of carbon dioxide produced:

The balanced equation for the combustion of propane can be written as,

$C_3{H}_8{}_{(g)}+5O_2{}_{(g)}\stackrel{}{\to }3C{O}_2{}_{(g)}+4H_2{O}_{(l)}$

The amount of ${\text{CO}}_{\text{2}}$ formed in this reaction can be calculated using number of moles of propane and stoichiometry of components.

The balanced equation shows a mole ratio of ${\text{3 moles CO}}_{\text{2}}{\text{ : 1 mole C}}_{\text{3}}{\text{H}}_{\text{8}}$

The amount of ${\text{CO}}_{\text{2}}$ produced is calculated as follows,

$\begin{array}{l}\text{Amount}\text{of}{\text{CO}}_{\text{2}}\text{=}\text{3}\text{.65}\text{mol}\text{of}\text{propane}\text{×}\frac{\text{3}\text{mol}\text{of}{\text{CO}}_{\text{2}}}{\text{1}\text{mol}\text{of}\text{propane}}\text{×}\frac{\text{44 g of}{\text{CO}}_{\text{2}}}{\text{1}\text{mol}\text{of}{\text{CO}}_{\text{2}}}\\ \text{=}\text{481}\text{.8}\text{g}\text{of}{\text{CO}}_{\text{2}}\end{array}$

Therefore, the amount of carbon dioxide produced is $481.8gofC{O}_2$

Conclusion

The amount of ${\text{CO}}_{\text{2}}$ produced by burning $\text{3}\text{.65 moles}$ of propane was calculated as $481.8gofC{O}_2$