Question

sandwich stoichiometry
part 1: cheese sandwiches
objective:

• go to the pbs simulation website: https://phet.colorado.edu/en/simulation/reactants-products-and-leftovers
• select “sandwiches” → select “meat, cheese” at the top.
• use the arrows to enter the following under reactants on the left (before reaction):

1. fill in the number of products and leftovers under “after reaction” in the table below.

before reaction
5 pieces of bread
5 slices of cheese
products
leftovers
after reaction

1. create a definition for “limiting reagent”, based on what you know about the words in the term.
2. create a definition for “excess reagent”, based on what you know about the words in the term.
3. from the example above, which is the limiting reagent?
4. from the example above, which is the excess reagent?
5. how many pieces of bread and how many pieces of cheese do you need to make exactly 3 sandwiches with no leftovers?

____ pieces of bread
____ pieces of cheese

1. complete the table. for every sandwich, you need __ slice of cheese and __ piece of bread.

therefore, the ratio is __ pieces of bread : slice of cheese : __ complete sandwiches
how many can you make if you have 6 pieces of bread?
part ii : meat and cheese sandwiches

• select “sandwiches” → select “meat and cheese” at the top.

1. fill in the number of products and leftovers under “after reaction” in the table below.

before reaction
5 pieces of bread
5 pieces of meat
5 slices of cheese
products
leftovers
after reaction

before reaction
8 pieces of bread
3 pieces of meat
4 pieces of cheese
products
leftovers
after reaction

(note: there may be more than one)
from the example above, which is the limiting reagent?
from the example above, which is the excess reagent?
(note: there may be more than one)
from the example above, which is the limiting reagent?
from the example above, which is the excess reagent?

1. create a ratio for the creation of a meat and cheese sandwich.
2. if you had five pieces of meat and six pieces of bread, with an excess of cheese, how many sandwiches could you make? what would be the limiting reagent?

Explanation:

Step1: Analyze Cheese Sandwich Data

Given: 8 bread, 6 cheese. 1 sandwich needs 2 bread, 1 cheese.
Max sandwiches from bread: $\frac{8}{2}=4$
Max sandwiches from cheese: $\frac{6}{1}=6$
Leftovers: Bread $8-(4\times2)=0$, Cheese $6-(4\times1)=2$

Step2: Define Limiting Reagent

Limiting reagent: Reactant fully consumed, limits product.

Step3: Define Excess Reagent

Excess reagent: Reactant left after reaction ends.

Step4: Identify Cheese Sandwich LR/ER

Limiting reagent: Bread (runs out first)
Excess reagent: Cheese (leftover)

Step5: Calculate Exact 3 Sandwiches

Bread needed: $3\times2=6$ pieces
Cheese needed: $3\times1=3$ pieces

Step6: State Cheese Sandwich Ratio

Ratio: 2 bread : 1 cheese : 1 sandwich

Step7: Predict from Cheese Sandwich Ratio

With 8 bread, 6 cheese: 4 sandwiches (limited by bread)

Step8: Analyze Meat Cheese Sandwich #1

Given: 5 bread, 5 meat, 5 cheese. 1 sandwich needs 2 bread, 1 meat, 1 cheese.
Max sandwiches from bread: $\frac{5}{2}=2$ (whole number)
Max from meat/cheese: $\frac{5}{1}=5$
Leftovers: Bread $5-(2\times2)=1$, Meat $5-(2\times1)=3$, Cheese $5-(2\times1)=3$
Limiting reagent: Bread; Excess: Meat, Cheese

Step9: Analyze Meat Cheese Sandwich #2

Given: 8 bread, 3 meat, 4 cheese.
Max sandwiches from bread: $\frac{8}{2}=4$; from meat: $\frac{3}{1}=3$; from cheese: $\frac{4}{1}=4$
Leftovers: Bread $8-(3\times2)=2$, Meat $3-(3\times1)=0$, Cheese $4-(3\times1)=1$
Limiting reagent: Meat; Excess: Bread, Cheese

Step10: State Meat Cheese Sandwich Ratio

Ratio: 2 bread : 1 meat : 1 cheese : 1 sandwich

Step11: Calculate 4 Meat, 6 Bread Sandwiches

Max from meat: $\frac{4}{1}=4$; from bread: $\frac{6}{2}=3$
Sandwiches: 3; Limiting reagent: Bread

Answer:

Part 1: Cheese Sandwiches

1.

Before Reaction	Products	Leftovers
6 pieces of cheese		2

1. Limiting reagent: The reactant that is completely used up first, which determines the maximum amount of product that can be formed.
2. Excess reagent: The reactant that is not completely used up and remains after the limiting reagent is consumed.
3. Limiting reagent: Pieces of bread
4. Excess reagent: Pieces of cheese
5. 6 pieces of bread, 3 pieces of cheese
6. For every sandwich, you need 1 slice of cheese and 2 pieces of bread.

Ratio: 2 pieces of bread : 1 slice of cheese : 1 complete sandwich
You can make 4 sandwiches.

Part 2: Meat and Cheese Sandwiches

8.

First Table

Before Reaction	Products	Leftovers
5 pieces of meat		3
5 pieces of cheese		3

Limiting reagent: Pieces of bread
Excess reagent: Pieces of meat, pieces of cheese

Second Table

Before Reaction	Products	Leftovers
3 pieces of meat		0
4 pieces of cheese		1

Limiting reagent: Pieces of meat
Excess reagent: Pieces of bread, pieces of cheese

1. Ratio: 2 pieces of bread : 1 piece of meat : 1 slice of cheese : 1 complete sandwich
2. You can make 3 sandwiches. The limiting reagent is pieces of bread.