Limiting Reactant II and Percent Yield A.K.A. Stoichiometry.

Limiting Reactant II and Percent Yield

A.K.A. Stoichiometry

The reactant that limits the amount of product produced

Limiting reactant is consumed fully in a chemical reaction

Excess reactant remains in a chemical reaction

What is a Limiting Reactant?

Remember The Sundae Example…

The chocolate syrup was consumed fully.The ice cream and cherries are left over.

Calculate using mass-mass conversion; find which reactant produces the least amount of product

Or use mole-mole conversion to determine which reactant is consumed first

How do we determine which reactant is the limiting

reactant?

What is the limiting reactant when 10.0 g of SiO2 react with 5.0 g of HF?

Create a conversion pathway using mass-mass conversion

SiO2(s) + 4 HF(l) → SiF4(g) + 2 H2O(l)

SiO2(s) + 4 HF(l) → SiF4(g) + 2 H2O(l)

SiO2 is the limiting reactant!

Limiting Reactant RelayTime for

How efficient is a chemical reaction?

Does the reaction go to completion?

How much product is produced?

How can we predict the amount of product produced?

How Does Sundae Production and Percent Yield Relate?

• If you made only 25 sundaes but You really needed 40, what was

your production yield?• Actual yield = 25 sundaes• Production (theoretical) yield = 40

sundaes• Percent yield = 25 x 100 % =

63% 40

5.00 g of Cu is mixed with an excess of AgNO3.

The reaction produces 15.2 g of Ag

What is the percent yield for this reaction?

We want to know how much product is produced?

Create your conversion pathway using mass-mass conversion

Cu + 2 AgNO3 2 Ag + Cu(NO3)2

17.0 g Ag is our theoretical yield; need to use it to calculate percent yield

Percent Yield

Percent Yield = Actual yield x 100

Theoretical yield

Actual/Theoretical

Percent Percent Yield

Percent Yield = 15.2 g Ag x 100 = 89.4 %

17.0 g Ag

Percent Yield WorksheetYour turn…

What is the percent yield when 24.8 g of CaCO3 decomposes to give 13.1 g CaO? CaCO3CaO + CO2

Plan your conversion pathwayUtilize mass-mass conversion

One more example

CaCO3CaO + CO2

The theoretical yield is 13.9 g of CaO; what is our percent yield? The reaction made 13.1 g CaO

Actual/Theoretical

Percent Percent Yield

= 13.1 g x 100 = 94.2 %

13.9 g

Exit TicketTime to fill out an

Read over Stoichiometry Lab carefully

Answer pre-laboratory questions

Homework