Chemistry 2014 S’more Stoichiometry
Name______________
In this activity, you will be introduced to simple stoichiometry. Stoichiometry is the chemical term to describe calculations that allow us to find the amounts of chemicals involved in a given reaction. In stoichiometry, you must always start with a balanced equation! We will use the following balanced recipe (equation):
2Gc + 1 M + 3C
Gc = graham cracker M = marshmallow
Gc2 MC3
C = chocolate squares Gc2 MC3 = S’more
1. If each student is to make one S’more, and I have 130 students, how much of each ingredient will I need? Show your work. Show your work using dimensional analysis. Example for graham crackers: 130 s’mores X 2 graham crackers = 260 graham crackers 1 s’more 2. If I have 20 graham crackers, how many marshmallows and chocolate pieces will I need to make S’mores? How many S’mores? Show your work using dimensional analysis. _____________ 3. You decide to make a large batch of S’mores. You have 85 chocolate pieces. How much of each other ingredient do you need? How many S’mores can you make? Round to the nearest whole number! Show your work using dimensional analysis. _____________ 4. How many S/mores can you make from these combinations?
2 Gc + 1 M + 4 C =
________ Smores
4 Gc + 2 M + 8 C =
________ Smores
10 Gc + 5 M + 20 C =
________ Smores
5. A reactant that is left over is said to be in excess and those that are used up limit the amount of product that can be made and are thus called limiting reactants. The maximum number of S’mores you could make is called the theoretical yield. For example, if you had 17 graham crackers, 7 marshmallows, and 20 chocolate pieces, what would the theoretical yield be? Which reactants are in excess and which are all used up and thus limiting reactants? Theoretical Yield_________ Excess Reactants_________ Limiting Reactants:_______
O’Ryan
2Gc + 1 M + 3C
Chemistry 2014
Gc2 MC3
Procedure: 1. Pick up 2 graham crackers, 1 marshmallow and 3 chocolate squares. 2. Using the masses provided, record the total mass of each reactant in the balance equation (recipe) below. 3. Break your graham cracker into 2 pieces and break your chocolate into 3 pieces. Put your chocolate onto 1 of your graham crackers. 4. Using a paperclip, roast your marshmallow over the Bunsen burner. DO NOT BURN! 5. Quickly place the marshmallow onto the chocolate pieces and cover it with your second graham cracker. Wait for it to cool and enjoy the sweet taste of success in chemistry! Masses of S’more ingredients
Gc 7.75
M 6.3
C 3.4
Data:
2Gc 2 Graham Cracker Squares ___________ grams (7.75 g ea.)
M 1 Marshmallow
3C 3 Chocolate Squares
Gc2 MC3 1 S’more
___________grams (6.3 g ea)
___________grams ….(3.4 g ea.)
___________grams
Questions: [Use a blank sheet of paper to show your work.] 1. What is the mass of 32 Gc2 MC3 ? _______________ 2. If you have 31.32 g of C, how many grams of M will you need? _________ 3. If you have 719.1 g of Gc how many grams of C will you need? _________ 4. If you have 114.4 g of M and excess C, how many Gc will you need? _______________
How many grams would this be?
5. If you have 108.5 g of Gc, how many grams of s’mores can you make? _____ 6. If you have 48 g of chocolate and excess marshmallow and graham crackers, how many
grams of S’mores can you make? ___________________________
7. What is the theoretical yield if you have 31 g of Gc, 75 g of M and 20.6 g of C?
_________________________________ If you have enough ingredients to make 3,806.25 grams of s’mores, but only end up with 3,714.9 g of s’mores, what is the percent yield? __________ How many s’mores are missing? __________________
O’Ryan
