Limiting Reactants and Yield Limiting Factors Limiting factors

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Limiting Reactants and % Yield

Limiting Reactants and % Yield

Limiting Factors Limiting factors are those factors which control the speed or the outcome

Limiting Factors Limiting factors are those factors which control the speed or the outcome of a reaction or a situation Ingredients for making “S’mores”: 2 graham crackers 1 marshmallow 1 Hershey bar How many “S’mores” can you make with 14 graham crackers, 5 marshmallows, and 6 Hershey bars? How many of each ingredient are left over?

Limiting Reactant The limiting reactant is the reactant which controls the rate of reaction

Limiting Reactant The limiting reactant is the reactant which controls the rate of reaction or the amount of product that can be made Excess The reactant that you have more than you need to perform a chemical reaction

Here’s an example You are making ham and cheese sandwiches and you have: 5

Here’s an example You are making ham and cheese sandwiches and you have: 5 pieces of ham 5 pieces of cheese 8 pieces of bread Which of these ingredients do you have more than enough of (excess reactant)? Which of these do you not have enough of (limiting reactant?

Now lets apply this to an equation… C 3 H 8 + O 2

Now lets apply this to an equation… C 3 H 8 + O 2 CO 2 + H 2 O 1. Balance the equation 2. How many moles of CO 2 are produced from 14. 8 g of C 3 H 8? 3. How many moles of CO 2 are produced from 3. 44 g of O 2? 4. If you mixed 14. 8 g C 3 H 8 with 3. 44 g O 2 , which would run out first? (In other words, which one is the limiting reagent? ). How do you know?

Yield is how much product that you produce Actual yield refers to the amount

Yield is how much product that you produce Actual yield refers to the amount of product that is actually generated (measured) Theoretical yield refers to the amount of product that you expect to generate (Calculated)

Theoretical vs. Actual Yield You recently bought a new car. The EPA sticker says

Theoretical vs. Actual Yield You recently bought a new car. The EPA sticker says that you should get 28 mpg in “average driving”. Your actual miles per gallon turns out to be less than 28 mpg. Why?

Theoretical Yield vs. Actual You perform a mass calculation to determine how much chemical

Theoretical Yield vs. Actual You perform a mass calculation to determine how much chemical should be produced in a reaction. The actual results of the experiment produce less chemical than calculated. Why?

Calculating Percent Yield 1. Calculate theoretical yield (mass-mass calculation). 2. Determine the actual yield.

Calculating Percent Yield 1. Calculate theoretical yield (mass-mass calculation). 2. Determine the actual yield. 3. Calculate the % yield % Yield = Actual yield x 100 Theoretical yield

A Percent Yield Problem C 3 H 8 + O 2 CO 2 +

A Percent Yield Problem C 3 H 8 + O 2 CO 2 + H 2 O 1. In an ideal situation, how many grams of CO 2 would be produced? (This is theoretical yield). 2. If this reaction was carried out and 2. 0 g of CO 2 were produced (This is the actual yield), what is the percent yield of CO 2?