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 |
Procedure/data:
- Use the 3 different reactants and one product to write a balanced equation for the making of s’mores
______2Gc______+ _____2M______ + ____4Cp____→ _Gc2 M2Cp2_
- What type of reaction would this be classified as? __________Physical reaction______
- 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.
- 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____%