Limiting Reagents

If you mix two chemicals together as reactants it is unlikely that both reactants will be used up completely when forming products. One will be used to completion, this one is the limiting reactant, and will limit how much product can be made. The other will be used up until the other reactant runs out and there will be some left over, so it is an excess reagent. 


If you have 8 cars and 48 tires, which one is limiting? Which one will you run out of first?

In this example it is easy to "see" which is the limiting and which is excess. When looking at quantities of chemicals it is not as easy to "see."

To determine which chemical is limiting, convert from the given reactants to a product (it does not matter which). Whichever reactant produces the least amount of product is limiting. 

4 NH3(g) + 5 O2(g)4 NO(g) + 6 H2O(g)

If you have 2.00 grams of ammonia and 4.00 grams of oxygen gas which is limiting?

Because the oxygen produced less of the product nitrogen monoxide, oxygen is limiting. 

Chemistry of Glow Sticks and Hydrogen Peroxide

Compound Interest's Original post about glow sticks can be found HERE; Hydrogen Peroxide can be found HERE.

For more information about chemiluminescence... read on.

Chemistry Of: Salicylic Acid and Aluminum Chlorohydrate

Here are the links for Compound Interest's original posts on Salicylic Acid and Aluminum chlorohydrate.

Video: Mental Floss: How does deodorant work? Worth a watch!

This TEDtalk about ethnobotany is also intriguing. And if you do not know what ethnobotany is, watch it!

How Advertisers Convinced Americans They Smelled Bad: A Smithsonian article about how the modern industry got started. 



Who knew there was any trivia about deodorant, much less a top twelve?!? Check it out here. My favorite is that it all started with the Egyptians, followed by the tip to never carry goats under your arms... 


And here is another one! Sex-specific deodorant is all in labeling and marketing! I knew it... and I have been wearing Old Spice for years. My new favorite scent is Amber. 

Chemistry Of: Nasal Decongestants and Vaccines

I cannot get the graphic for decongestants to load, but you can download it here. 

Not so long ago, most children did not make it to adulthood. Interested in how well vaccines work? Check out this graphic of death rates prior to vaccination versus recent cases.

The original post for Vaccines at Compound Interest can found here; for nasal decongestants, here. 

There are so many great TED and TEDEd videos on germs, diseases, and vaccines. Please take a minute to watch one!

• How do germs spread and why do they make us sick? HERE
• How do vaccines work? HERE
• Demo: A needle free vaccine HERE
• How we conquered the deadly smallpox virus HERE
• How we will stop Polio for good HERE
• My wish: Help me stop pandemics HERE

Also, an interesting game for your Smartie Phones and this topic is Plague, Inc. available on Itunes and Android. More information can be found here.