Fizzy Drink Stoichiometry

Last year I stumbled across a lab for stoichiometry that has students create carbonated Kool-Aid by combining food grade citric acid and baking soda in their drink.  It worked beautifully, and we completed it again today.  I bought four packets of generic fruit punch drink mix, a bag of sugar, one box of baking soda, plastic spoons, cupcake paper wrappers for measuring the powders on the balance, enough red plastic cups for each team to have one, and enough small Dixie cups for each student to have one.  The food grade citric acid was a bit harder to find.  I called around to grocery stores after reading that it was used in canning, but no local shop had it in stock.  They sweetly offered to order it for me, but I figured I could do that myself.  I ended up purchasing a small jar online.  Each team of four students uses less than one gram, so the 100+ gram small jar is more than enough, and not expensive at all. Citric Acid


Students first taste the drink alone, drink + citric acid, then drink + baking soda.  It's a very dramatic response when they taste them.  I always stress that no one is required to eat/drink anything they don't wish to, but I encourage them to try it if they feel comfortable doing so. 

The final part of the experiment is to

1) write a balanced equation for the reaction between citric acid and baking soda
2) calculate the quantity of baking soda that would react completely with 0.30 g citric acid.
3) mix your calculated quantities together in the drink.  If calculations are correct it's lovely and bubbly, but not sour or salty.
4) answer analysis questions about the work, including several more three step stoic problems leading toward the idea of limiting reactants.

 I'm very happy with the science involved, the dramatic student interest, and the content ties to real life in such a simple way.  I think this lab will be a winner for years to come.


The activity HERE is very similar to what I use, although I've modified the questions to suit my curriculum.