Question

Which one produces more heat on combustion - one-mole methane or one-mole propane?

Answer 1

Step 1: Introduction

The combustion of hydrocarbon is to give Carbon dioxide $\left({\mathrm{CO}}_2\right)$ and Water $\left({\mathrm{H}}_2\mathrm{O}\right)$ and evolve a large amount of heat is called a combustion reaction.

A combustion reaction is an exothermic reaction.

Step 2: Combustion reaction of Methane:

The combustion reaction of Methane $\left({\mathrm{CH}}_4\right)$ is:

$$\begin{gathered} {\mathrm{CH}}_4+2{\mathrm{O}}_2\to {\mathrm{CO}}_2+2{\mathrm{H}}_2\mathrm{O}+890\mathrm{KJ} \\ \left(\mathrm{Methane}\right)\left(\mathrm{Oxygen}\right)(\mathrm{Carbon}(\mathrm{Water})\mathrm{Heat} \\ \mathrm{dioxide}) \end{gathered}$$

Step 3: Combustion reaction of Propane:

The combustion reaction of Propane $\left({\mathrm{C}}_3{\mathrm{H}}_8\right)$ is:

$$\begin{gathered} {\mathrm{C}}_3{\mathrm{H}}_8+5{\mathrm{O}}_2\to 3{\mathrm{CO}}_2+4{\mathrm{H}}_2\mathrm{O}+2670\mathrm{KJ} \\ \left(\mathrm{Propane}\right)\left(\mathrm{Oxygen}\right)(\mathrm{Carbon}(\mathrm{Water})\mathrm{Heat} \\ \mathrm{dioxide}) \end{gathered}$$

Therefore, one mole of Propane produces more heat than one mole of Methane.