S‛moles of S‛mores Lab
Name: ____________________ Introduction : Have you ever made a recipe and found that you were low on one ingredient you needed? Could you still make the recipe? How much could you make? The same situation exists for chemical reactions. In order to make the desired amount of product we must have enough of each reactant. A reactant that is left over is said to be in EXCESS . A reaction that is used up entirely and limits the amount of product that can be produced is called a LIMITING REACTANT . This lab will introduce the concepts and vocabulary mentioned above through s’mores. Materials : Chocolate Bars
Marshmallow (M)
Graham Crackers 1 bar = C 12
1­whole graham cracker = G 4 1 piece = C
¼ of a whole graham cracker = G Designated Bunsen Burner
Skewer
Paper Towel Procedure : 1) Answer all of the calculations. *Show Work!! 2) Show your calculations to Ms. Biersdorf before starting the lab. 3) AFTER all questions are deemed correct, you may make a s’more. a) Wash hands before and after making your s’more b) Obtain materials for a s’more; place all on a paper towel ­ Don’t put anything directly on the counters! c) Roast a marshmallow using the setup bunsen burners and build/eat a s’more. 4) Dispose of all waste in a garbage can and clean­up any messes. Calculations : 1) Write the balanced recipe (equation) for a s’more [G 2 MC 3 G 2 ] using chocolate bars (C 12 ), marshmallows (M), and graham crackers (G 4 ) as the three reactants: 2) Using the balanced recipe (equation), write the 12 mole ratios: 3) If each student is to make one s’more and I have 120 students, how much of each ingredient will I need? *Show work a) G 4 __________ b) C 12 __________ c) M ____________ 4) If you had an eight bar pack of chocolate: *Show work for each part a) How many graham crackers would you need in order to make as many s’mores as possible? 1 b) How many marshmallows? c) How many total s’mores would you have? 5) Use the following list of ingredients to answer the questions below: 20 C12 ; 40 M ; 35 G 4 a) Which ingredient will you run out of first? *Show work (This is the limiting reactant) b) What is the maximum number of complete s’mores you can make? *Show work c) How much of each excess ingredient will be left over after the s’mores are made? *Show work 6) One graham cracker (G 4 ) has a mass of 13.7 grams. The mass found on the front of the graham cracker box is 454 grams. a) How many graham crackers are in the box? *Show work b) How many s’mores can be made by using one box of graham crackers? *Show work 7) When a marshmallow is cooked over a fire it goes through a combustion reaction. The sucrose (C 12 H 22 O 11 ) in the marshmallow reacts with oxygen gas in the air when heat is added to the system. The final products are carbon dioxide and water. Use the chemical reaction below to answer the following questions: __ C 12 H 22 O 11 + __ O 2 → __ CO 2 + __ H2 O a) Balance the chemical reaction equation. b) Convert 1 2.0 g of sucrose to grams of carbon dioxide. c) Convert 12.0 g of oxygen gas to carbon dioxide. d) Which reactant, sucrose or oxygen gas, converted to the smallest amount of carbon dioxide? *This reactant is the limiting reactant e) Which reactant, sucrose or oxygen gas, converted to the largest amount of carbon dioxide? *This reactant is in excess. 2