ii. stoichiometry in the real world stoichiometry – unit. 10
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II. Stoichiometry in the Real World
II. Stoichiometry in the Real World
Stoichiometry – Unit. Stoichiometry – Unit. 1010
Stoichiometry –
Quantitative measurements between Reactants used and Products formed in chemical reaction
(Law of Conservation of Mass)
Do NowDo NowDo NowDo Now
Victoria Sandwich Cake recipe: 1 cup of Self Rising Flour ½ cup of Sugar ½ cup of Margarine 1tsp of baking powder 4 eggs
What is the ratio of flour to sugar?
What is the ratio of baking powder to Margarine?
Relationship derived from a balanced Relationship derived from a balanced EquationEquationRelationship derived from a balanced Relationship derived from a balanced EquationEquation
Iron + Oxygen Iron (III) Oxide
4Fe + 3O2 2Fe2O3
4 molsFe 3 mols O2 2 mols Fe2O3
223g/mol 93g/mol 319.4g/mol
Example:Example:Example:Example:
C3H8 (aq) + O2(aq) CO2 + H2O
=
C. Johannesson
A. Limiting ReactantsA. Limiting ReactantsA. Limiting ReactantsA. Limiting Reactants
Available IngredientsAvailable Ingredients• 1 pack of Hot dogs rolls (8rolls)• 1 pack of Hot dogs (6 dogs)
Limiting Reactant ?Limiting Reactant ?
Excess Reactants ?Excess Reactants ?
A. Limiting ReactantsA. Limiting ReactantsA. Limiting ReactantsA. Limiting ReactantsLimiting 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
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
Calculating the Amount of Calculating the Amount of ProductProductCalculating the Amount of Calculating the Amount of ProductProduct
Grams Convert Mole Ratio Convert Product(Grams)
(GIVEN ) to Moles to Grams (ASKED)
A. Limiting ReactantsA. Limiting ReactantsA. Limiting ReactantsA. Limiting Reactants
79.1 g of zinc react with 0.90 L of 2.5M HCl. Identify the limiting and excess reactants. How many liters of hydrogen are formed at STP?
Zn + 2HCl ZnCl2 + H2 79.1 g ? L0.90 L
2.5M
A. Limiting ReactantsA. Limiting ReactantsA. Limiting ReactantsA. Limiting Reactants
79.1g Zn
1 molZn
65.39g Zn
= 27.1 L H2
1 molH2
1 molZn
22.4 LH2
1 molH2
Zn + 2HCl ZnCl2 + H2 79.1 g ? L0.90 L
2.5M
A. Limiting ReactantsA. Limiting ReactantsA. Limiting ReactantsA. Limiting Reactants
22.4L H2
1 molH2
0.90L
2.5 molHCl
1 L= 25 L
H2
1 molH2
2 molHCl
Zn + 2HCl ZnCl2 + H2 79.1 g ? L0.90 L
2.5M
C. Johannesson
A. Limiting ReactantsA. Limiting ReactantsA. Limiting ReactantsA. Limiting Reactants
Zn: 27.1 L H2 HCl: 25 L H2
Limiting reactant: HCl
Excess reactant: Zn
Product Formed: 25 L H2
left over zinc
B. Percent YieldB. Percent YieldB. Percent YieldB. Percent Yield
100yield ltheoretica
yield actualyield %
calculated on paper
measured in lab
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
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:
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