Wednesday, October 25, 2006

My Sincerest Apologies

Devoted "She Blinded Me with Science" reader Ryan kindly pointed out that I didn't mention Mole Day, which happened on October 23rd. Shame on me. Ryan, did you play "Avogadro's Element Hunt"? It's on yesterday's link to the National Chemistry Week site. The mole is a fundamental unit of measurement in chemistry that lets us relate mass (something we can measure in the laboratory) to an amount of atoms or molecules (which we can't). When following chemical recipes, it's important to get the ratios of ingredients (molecules) correct. The "mole concept" is an extremely valuable tool that I use every day.
And now, for something completely different. One of the first things I learned about in Dr. Pearsall's Intermediate Inorganic Chemistry course was zinc phosphide, AKA "mole killer".

Here's how it works:
Zn3P2(s) + 6 HCl(aq) ---> 3 ZnCl2(aq) + 2 PH3(g)

Zinc phosphide reacts with the water and acid in the digestive system, where it breaks down to zinc chloride and phosphine gas. Nice favorable reaction, entropy increases due to gas formation, yadda yadda.

I had scribbled in the margin of my notebook that day and it reads: phosphine, spontaneously flammable in air or moles. I also imagine that a rapidly expanding gas wouldn't be good for the circulatory system, either.
See here for a little more zinc phosphide backstory and information about other rodenticides.


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