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S’mores Lab: Limiting Reactant
Name ____________________________ Date ____ Pd ___
Table # __________
Objective: You will assemble the maximum number of s’mores with the reactants at your table. You will
determine the limiting reactant and the excess reactants.
Background: S’mores are a tasty concoction of marshmallows and chocolate sandwiched between graham crackers.
Ordinarily, the marshmallows are roasted in an open flame. Since laboratory burners are unacceptable for the cooking
of food, we must use a hot plate instead, using a heavy foil pan (exclusively for food). You will need to bring a spatula or
flipper to turn your creations.
2 graham crackers + 1 piece of Hershey’s chocolate + 3 mini marshmallows  1 s’more
___ Gc + ___ Hc + ____ Mm  _____ Gc2HcMm3
Procedure:
1. Wash your hands.
2. Observe the numbers of each reactant listed on the strip of paper at your table. Count out and record the
number of “moles” of each reactant in the data chart below. Each piece represents a mole.
3. Determine the mass of 1 mole of each reactant as follows: Place a piece of paper towel on the balance, zero it
out, and then add the food. Do NOT place food directly on the balance. Record masses in chart below.
4. Assemble the maximum number of s’mores, using ONLY the #s of each reactant listed on the paper strip at
your table. Record the max # of s’mores in the data chart below. Also record limiting and excess reactants.
5. Set the large hot plate control to low (2 – 3), and adjust up slowly if needed. Small hotplates should be set to
4 – 5. Each hot plate is a bit different. Do not exceed level 5 or you will burn it quickly! Use your spatula/flipper
to turn the s’more. When they are cooked to your liking, go ahead and eat! You may make more as your
supplies and time allow.
Data Chart:
Graham cracker
# mol of Gc =
1 mol = 1 rectangle =
g/mol
Hershey’s chocolate
# mol of Hc =
1 mol = 1 piece =
g/mol
Mini marshmallow
# mol of Mm =
1 mol = 1 piece =
g/mol
Max number of s’mores assembled = ________________
Limiting reactant = _______________________________
Excess reactant(s) = ___________________________________________________________
Observations:
1. Which reactant softens/melts the quickest? ________________________________________
2. Briefly explain why. Address the composition, physical structure, and heat transfer ability of the marshmallow
and the chocolate.
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
Questions:
1. Define limiting reactant: _______________________________________________________________
2. Define excess reactant:________________________________________________________________
3. Write down the grams used of your limiting reactant: ____________________________________
4. Calculate the grams used of your two excess reactants in this lab, based on the limiting reactant.
5. Determine the grams left over for each excess reactant.
6. Using the “molar masses” from your lab data table, determine the limiting reactant and the maximum
number of s’mores you could make, given 454.0 grams (1 pound) of each reactant. Show work!
Limiting reactant?
7.
___________________________Number of s’mores? __________________________
Write and balance the chemical equation for the reaction between magnesium metal and hydrochloric
acid:
_____________________________________________________________________ redox? (yes or no)
If magnesium is the limiting reactant, what substances would you expect to find in the reaction
container when the reaction is complete? Assume a sealed container.
____________________________________________________________________________________