Cooking with Chemistry “Let’s Make a Cake”

2 Necessary Definitions Limiting Reactant: the reactant that runs out first and thus limits the amounts of products that can form Excess Reactant: the reactant that is not completely consumed in the reaction

Recipe for 1 CAKE 2 cups flour 2 eggs 1 cup sugar 1 ½ Tbsp. baking powder 1 cup water 1/3 cup oil (Mix all ingredients and bake until done)

Let’s check to see what we have in our kitchen… 10 cups of flour 7 cups of sugar 2 1/3 cups of oil 7 eggs 15 Tbsp. baking powder unlimited water (indoor plumbing)

Use the recipe and the amounts available in our kitchen to answer the following questions… How many cakes can be made? What is the limiting ingredient? Recipe for 1 CAKE 2 cups flour 2 eggs 1 cup sugar 1 ½ Tbsp. baking powder 1 cup water 1/3 cup oil (Mix all ingredients and bake until done)

Use the recipe and the amounts available in our kitchen to answer the following questions… How many cakes can be made? What is the limiting ingredient? The recipe card has the conversions. What’s in your kitchen is the given. Recipe for 1 CAKE 2 cups flour 2 eggs 1 cup sugar 1 ½ Tbsp. baking powder 1 cup water 1/3 cup oil (Mix all ingredients and bake until done) 10 cups of flour 7 cups of sugar 2 1/3 cups of oil 7 eggs 15 Tbsp. baking powder unlimited water (indoor plumbing)

10 cups flour 1 cake 1cake = 2 cups of flour Start with the flour. Write the amount in your kitchen in the first spot and use the amount needed for one cake to turn flour into cake. In the conversion spot, make sure amount of flour is on the bottom and cake is on the top. You can also use a proportion and cross multiply. 10 cups flour 1 cake 1cake = 2 cups of flour 2 cups of flour x 10 cups of flour Repeat process for all the ingredients. Recipe for 1 CAKE 2 cups flour 2 eggs 1 cup sugar 1 ½ Tbsp. baking powder 1 cup water 1/3 cup oil (Mix all ingredients and bake until done) 10 cups of flour 7 cups of sugar 2 1/3 cups of oil 7 eggs 15 Tbsp. baking powder unlimited water (indoor plumbing)

2Tires + 1Frame = 1Bicycle The Bicycle Factory… If I have 16 Tires & 7 Frames how many bicycles can be made, and what pieces will be left over?

The conversion is below: 2Tires + 1Frame = 1Bicycle Given: 16 Tires & 7 Frames how many bicycles can be made, and what pieces will be left over? Convert both tires and frames to bikes. Figure out what is the limiting (smaller amount of bikes) and what is the excess (larger amount of bikes) Subtract: excess bikes – limiting bikes Convert this number back to the part in excess. Given is bikes that remain but the conversion is the same, just upside down. You can also solve with a proportion.

A chemical reaction is similar to a recipe…

A chemical reaction is similar to a recipe…

We can make more than the recipe calls for…

We can make more than the recipe calls for…

We can use any starting amount (and have some items left over)… H2 + F2 2HF 6 mol of H2 are reacted with 4 mol of F2. Find the limiting reactant and the moles of product formed. Then subtract excess product – limiting product to get how much remains and convert back to the excess reactant. The balanced chemical reaction is like the recipe card. It has the conversion factors. The given amounts are in the box above. It is just like the cake and the bikes but with chemicals. The balanced equation tells us that 1 mole of H2 produces 2 moles of HF and 1 mole of F2 produces 2 moles of HF

We can use any starting amount (and have some items left over)… H2 + F2 2HF 6 mol of H2 are reacted with 4 mol of F2. Find the limiting reactant, the moles of product formed, and the moles of excess reactant remaining after the reaction.

We can use any starting amount (and have some items left over)… H2 + F2 2HF 6 mol of H2 are reacted with 4 mol of F2. Find the limiting reactant, the moles of product formed, and the moles of excess reactant remaining after the reaction.

SiO2 + 4HF  SiF4 + 2H2O 3.2 mol of SiO2 is reacted with 15.1 mol of HF. How many moles of water will form? What is the limiting reactant? What is excess reactant? How much of the excess remains after the reaction? Remember: the balanced equation gives you the conversion factors. Convert each reactant into moles of water. The lowest amount of water comes from the limiting reactant.

2NH3(g) + 3CuO(s)  N2(g) + 3Cu(s) + 3H2O(g) Nitrogen gas can be prepared by passing gaseous ammonia over solid copper(II) oxide at high temperatures. The other products of the reaction are solid copper and water vapor. How many moles of N2 are formed when 1.1 moles of NH3 is reacted with 1.2 moles of CuO? 2NH3(g) + 3CuO(s)  N2(g) + 3Cu(s) + 3H2O(g)   First find the limiting reactant by changing each reactant into moles of N2. Then report how much N2 is formed (smallest amount) Then subtract excess-limiting to get remaining amount Lastly, convert remaining amount back to excess reactant.

2H2 + O2 2H2O When 25.8 moles of O2 react with 7.55 moles of H2, how many moles of H2O will be produced? What is the limiting reactant? The excess reactant? How much of the excess reactant will remain? First find the limiting reactant by changing each reactant into moles of H2O. Then report how much H2O is formed (smallest amount) Then subtract excess-limiting to get remaining amount Lastly, convert remaining amount back to excess reactant.

4NH3 + 5O2  4NO + 6H2O If 0.44 moles NH3 are reacted with 0.3 moles of O2 how many moles of water will form? What is the limiting reactant? How many moles of the excess reactant will remain? First find the limiting reactant by changing each reactant into moles of H2O. Then report how much H2O is formed (smallest amount) Then subtract excess-limiting to get remaining amount Lastly, convert remaining amount back to excess reactant.