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April 2019 Limerick Project

Combustion Reactions

“A process denoted combustion
Results in methodic production:
H2O, CO2;
Common products ensue
From a fuel hydrocarbon’s consumption.”

As with the April 5 limerick, the 6 April 2019 limerick addresses another reaction class and how to easily identify it. This specific poem examines combustion reactions and the chemical formulas used to represent specific compounds involved therein.    

“A process denoted combustion/ Results in methodic production:”
This limerick outlines the class of reaction of interest, pointing out that we’ll be able to classify a reaction as a combustion reaction by looking at its characteristic reactants and products (its “methodic production”). The remainder of the poem defines these species more directly.      

“H2O, CO2;/ Common products ensue/
From a fuel hydrocarbon’s consumption.”  
This is the first limerick in my project to exploit chemical notation to obey the rhythmic rules of the poetic form! For the syllables to work here, the third line is read as “H two O, C O two.”  These abbreviations have specific meanings for chemists.

Notably, “H2O” and “CO2” are not formatted correctly, due to Twitter constraints (or at least my lack of knowledge of how to format subscripts and superscripts via that medium!); they should be properly written as H2O and CO2.  These are the chemical formulas for water and carbon dioxide, respectively. The formula for water tells us that each H2O molecule contains two hydrogen atoms and one oxygen atom; the formula for carbon dioxide tells us that each CO2 molecule contains one carbon atom and two oxygen atoms. 

Water and carbon dioxide are the characteristic products when a hydrocarbon fuel [a molecule consisting only of carbon and hydrogen, such as butane (C4H10) or propane (C3H8)] reacts with oxygen to undergo combustion.        

The overall pattern can be seen in the balanced reaction shown below, which represents the complete combustion of propane. 
C3H8 + 5 O2 →  3 CO2 + 4 H2O