Limiting Reactant

Description:  In this phenomenon both magnesium metal and hydrochloric acid are limiting reactants.  I have used this in a chemistry class, framing it as "The Case of the Mixed Up Masses".  I tell them that I added varying amounts of magnesium metal but I forgot to label the flasks.  If done correctly they should get the curve seen below.  I learned about this on the NSTA Resource page.  

Web Resource:  NSTA Stoichiometry Balloon Race

Professor Jim Holler of the University of Kentucky demonstrates the concept of limiting reactants with magnesium and hydrochloric acid.