Propane Combustion for Dummies

Propane molecule C3H8

We aren't sure whether it's hilarious or disheartening, but some of our most fascinating DotD nominations go to the content written by liberal arts majors trying to answer simple science questions. Bless their hearts, the guys and gals just don't know when they're getting it wrong, not to mention the many times their attempts to reword even slightly technical literature get downright ridiculous. We have one of those today, eHowian Brenda Priddy who attempted to tackle "Why Burning Propane Makes Water" at Sciencing.com.

We don't know whether Priddy took introductory chemistry while getting her AA in English, but we rather doubt it based on this sample of her output. For starters, let's look at her definition of propane:

"Propane is a gas that's produced during petroleum production. Propane is a three-carbon alkane (a molecule composed of three carbons and five hydrogen atoms)."

Well, Brenda, in the first place propane is not "produced during petroleum production" – it's a component of natural gas. In the second place, propane's formula is C₃H₈; C₃H₅ is the formula for an allyl radical. Having botched that definition, Brenda moved on to "explain" to her readers that

"The formation of water is produced by a combination of oxygen, propane and carbon dioxide during the combustion process..."

...which would surprise most chemists, since carbon dioxide is a byproduct of combustion, just like water. In fact, Priddy (carefully and, unfortunately, incorrectly) copied the chemical reaction for combustion of propane (in an oxygen-rich environment) C3H8 + 5O2 = 3CO2 + 4H2O while apparently unaware of the significance of the position of CO2 relative to the equals sign. Brenda continued to mangle the most basic chemistry with her description of this reaction:

"Propane's three-carbon alkane (3CH8) is added to five molecules of oxygen (O5). When heat is applied to the mixture, combustion occurs, and the atoms begin to interact violently. The electrons and protons push and pull on each other until balance is restored, creating carbon dioxide (3CO2) and water (4H2O). This process is continued until the propane, oxygen or heat is exhausted. The combustion of propane then results in the creation of relatively large amounts of water..."

...which has so many mistakes we haven't room to discuss them all in this space. We'll concentrate on one: Priddy thought that the addition of heat causes this reaction: it's significant that she didn't seem to understand the meaning of the word "combustion"; significant enough to award Brenda another Dumbass of the Day trophy. What an idiot!

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