c. johannesson ii. stoichiometry in the real world (p. 288-294) stoichiometry – ch. 9

C. Johannesson

II. Stoichiometry in the Real World

(p. 288-294)

II. Stoichiometry in the Real World

(p. 288-294)

Stoichiometry – Ch. 9Stoichiometry – Ch. 9

C. Johannesson

A. Limiting ReactantsA. Limiting ReactantsA. Limiting ReactantsA. Limiting Reactants

Available IngredientsAvailable Ingredients• 4 slices of bread• 1 jar of peanut butter• 1/2 jar of jelly

Limiting ReactantLimiting Reactant• bread

Excess ReactantsExcess Reactants• peanut butter and jelly

C. Johannesson

A. Limiting ReactantsA. Limiting ReactantsA. Limiting ReactantsA. Limiting Reactants

Limiting ReactantLimiting Reactant• used up in a reaction• determines the amount of product

Excess ReactantExcess Reactant• added to ensure that the other

reactant is completely used up• cheaper & easier to recycle

C. Johannesson

A. Limiting ReactantsA. Limiting ReactantsA. Limiting ReactantsA. Limiting Reactants

1. Write a balanced equation.

2. For each reactant, calculate the

amount of product formed.

3. Smaller answer indicates:

• limiting reactant

• amount of product

C. Johannesson

A. Limiting ReactantsA. Limiting ReactantsA. Limiting ReactantsA. Limiting Reactants

79.1 g of zinc react with 81g HCl. Identify the limiting and excess reactants. How many grams of hydrogen are formed at STP?

Zn + 2HCl ZnCl2 + H2 79.1 g ? L0.90 L

2.5M

C. Johannesson

A. Limiting ReactantsA. Limiting ReactantsA. Limiting ReactantsA. Limiting Reactants

79.1g Zn

1 molZn

65 g Zn

= 2.4 g H2

1 molH2

1 molZn

2gH2

1 molH2

Zn + 2HCl ZnCl2 + H2 79.1 g ? g81.0g

C. Johannesson

A. Limiting ReactantsA. Limiting ReactantsA. Limiting ReactantsA. Limiting Reactants

2g H2

1 molH2

81.Og

1 molHCl

36g= 2.3 g

H2

1 molH2

2 molHCl

Zn + 2HCl ZnCl2 + H2 79.1 g ? g81.0 g

C. Johannesson

A. Limiting ReactantsA. Limiting ReactantsA. Limiting ReactantsA. Limiting Reactants

Zn: 2.4 g H2 HCl: 2.3 gH2

Limiting reactant: HCl

Excess reactant: Zn

Product Formed: 2.3 g H2

left over zinc

C. Johannesson

B. Percent YieldB. Percent YieldB. Percent YieldB. Percent Yield

100yield ltheoretica

yield actualyield %

calculated on paper

measured in lab

C. Johannesson

B. Percent YieldB. Percent YieldB. Percent YieldB. Percent Yield

When 45.8 g of K2CO3 react with excess

HCl, 46.3 g of KCl are formed. Calculate the theoretical and % yields of KCl.

K2CO3 + 2HCl 2KCl + H2O + CO2 45.8 g ? g

actual: 46.3 g

C. Johannesson

B. Percent YieldB. Percent YieldB. Percent YieldB. Percent Yield

45.8 gK2CO3

1 molK2CO3

138.21 gK2CO3

= 49.4g KCl

2 molKCl

1 molK2CO3

74.55g KCl

1 molKCl

K2CO3 + 2HCl 2KCl + H2O + CO2 45.8 g ? g

actual: 46.3 g

Theoretical Yield:

C. Johannesson

B. Percent YieldB. Percent YieldB. Percent YieldB. Percent Yield

Theoretical Yield = 49.4 g KCl

% Yield =46.3 g

49.4 g 100 =93.7%

K2CO3 + 2HCl 2KCl + H2O + CO2 45.8 g 49.4 g

actual: 46.3 g