ii. stoichiometry in the real world (p. 379 – 388) stoichiometry – ch. 11
TRANSCRIPT
II. Stoichiometry in the Real World
(p. 379 – 388)
Stoichiometry – Ch. Stoichiometry – Ch. 1111
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
A. Limiting ReactantsA. Limiting ReactantsA. Limiting ReactantsA. Limiting Reactants
Available IngredientsAvailable Ingredients• 24 graham cracker squares• 1 bag of marshmallows• 12 pieces of chocolate
Limiting ReactantLimiting Reactant• chocolate
Excess ReactantsExcess Reactants• Marshmallows and graham
crackers
A. Limiting ReactantsA. Limiting ReactantsA. Limiting ReactantsA. Limiting Reactants
Limiting ReactantLimiting Reactant• one that is used up in a reaction• determines the amount of product that
can be produced
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 the balanced equation.
2. For each reactant, calculate the
amount of product formed.
3. Smaller answer indicates:
• limiting reactant
• amount of product actually possible
A. Limiting ReactantsA. Limiting ReactantsA. Limiting ReactantsA. Limiting Reactants
79.1 g of zinc react with 68.1 g HCl. Identify the limiting and excess reactants. How many grams of hydrogen can be formed?
Zn + 2HCl ZnCl2 + H2 79.1 g ? g68.1 g
A. Limiting ReactantsA. Limiting ReactantsA. Limiting ReactantsA. Limiting Reactants
79.1g Zn
1 molZn
65.39g Zn
= 2.44 g H2
1 molH2
1 molZn
2.02 gH2
1 molH2
Zn + 2HCl ZnCl2 + H2 79.1 g ? g68.1 g
A. Limiting ReactantsA. Limiting ReactantsA. Limiting ReactantsA. Limiting Reactants
2.02 g H2
1 molH2
68.1g HCl
1 molHCl
36.46 g HCl
= 1.89 g H2
1 molH2
2 molHCl
Zn + 2HCl ZnCl2 + H2 79.1 g ? g68.1 g
A. Limiting ReactantsA. Limiting ReactantsA. Limiting ReactantsA. Limiting Reactants
Zn: 2.44 g H2 HCl: 1.89 g H2
Limiting reactant: HCl
Excess reactant: Zn
Product Formed: 1.89 g H2
left over zinc
A. Limiting Reactants #2A. Limiting Reactants #2A. Limiting Reactants #2A. Limiting Reactants #2
5.42 g of magnesium ribbon react with 4.00 g of oxygen gas. Identify the limiting and excess reactants. How many grams of magnesium oxide are formed?
2Mg + O2 2MgO 5.42 g ? g4.00 g
A. Limiting Reactants #2A. Limiting Reactants #2A. Limiting Reactants #2A. Limiting Reactants #2
5.42g Mg
1 molMg
24.31g Mg
= 8.99 g MgO
2 molMgO
2 molMg
40.31 gMgO
1 molMgO
2Mg + O2 2MgO
5.42 g ? g4.00 g
A. Limiting Reactants #2A. Limiting Reactants #2A. Limiting Reactants #2A. Limiting Reactants #2
40.31g MgO
1 molMgO
4.00g O2
1 molO2
32.00 g O2
= 10.1 g MgO
2 molMgO
1 molO2
2Mg + O2 2MgO
5.42 g ? g4.00 g
A. Limiting Reactants #2A. Limiting Reactants #2A. Limiting Reactants #2A. Limiting Reactants #2
Mg: 8.99 g MgO O2: 10.1 g MgO
Excess oxygen
Limiting reactant: Mg
Excess reactant: O2
Product Formed: 8.99 g MgO
A. Limiting ReactantsA. Limiting ReactantsA. Limiting ReactantsA. Limiting Reactants
What other information could you find in these problems?
• How much of each reactant is used – in grams, liters, moles
• How much of excess reactant is left over – in grams, liters, moles
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.