Eating S’more While Learning about Limited and Excess Reactant

To deepen our understanding of limited and excess reactant, and percent and theoretical yield our learning facilitator made a s’more lab for us to experiment with. In order to complete the lab, I have to understand some of the terminologies such as limited reactant, excess reactant, theoretical yield, and percent yield.

Limiting Reactant- the reactant gets used up in a chemical reaction

Excess Reactant- the reactant that is left-over in a chemical reaction

Theoretical Yield: The maximum amount of product that can be produced.

Actual (experiment) yield: The actual yield is the quantity of a product that is obtained from a chemical reaction.

Percent Yield: Percent yield shows how effective the reaction is.   

Now let’s check out the lab note:

Problem:  Given a certain quantity of marshmallows, graham crackers, and chocolate pieces, what is the maximum number of S’mores that can be made?  Then figure out your percent yield!

Substance Symbol
Graham Cracker (half of a cracker) Gc
Marshmallow M
Chocolate Piece (individual piece of chocolate) Cp
S’more  (2 crackers, 2 pieces of chocolate, 2 marshmallows) Gc2MCp2


  1.  Use the 3 different reactants and one product to write a balanced equation for the making of s’mores

______2Gc______+ _____2M______   + ____4Cp____→ _Gc2 M2Cp2_  

  1. What type of reaction would this be classified as? __________Physical reaction______
  2.  Record the total moles (pieces) of each reactant available at your table

Graham Cracker (Gc)-  ___2pieces____     Marshmallow (M)-  __2pieces__              Chocolate Pieces (Cp)-_4pieces_

  • What is the maximum number of s’mores that your group can make?   ____3 s’smores____
  • Why?______Because we have a total of 6 crackers, 8 marshmallow, and 6 chocolate pieces. In order, to make one s’mores we require two pieces from each reactant so after a calculation, the maximum would be 3 s’mores.
  • Which reactant/s is/are limiting?  (the one/s that you will run out of first) :____The limiting reactants are the cracker and the chocolate pieces.
  • Which reactant/s is/are  in excess (the one/s that will be left over)___________The excess reactant is 2 marshmallows.


  1. Find the mass of one of each of the individual reactants (first zero a napkin and then find the mass on top of the napkin)


Graham Cracker (Gc)-  ___8g____ Marshmallow (M)-  ___5_____ g Chocolate Piece (Cp)-____3___ g

(one halfs of Gc)                (one single marshmallow)                  (one single chocolate piece)

  • Record the theoretical yield/mass of a S’more (Gc2M2Cp2) using your reactants (you can add them together)

                                    = ________32_________g

  • The ACTUAL (experimental) mass of one s’mores: ______30__________g
  • Find the percent yield of your s’mores:.      

                                    percent yield=____93.75____%



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