solving a stoichiometry problem 1.balance the equation. 2.convert given to moles. 3.determine which...
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Solving a Stoichiometry Solving a Stoichiometry ProblemProblem
1.1. Balance the equation.Balance the equation.
2.2. Convert given to moles.Convert given to moles.
3.3. Determine which reactant is limiting.Determine which reactant is limiting.
4.4. Use moles of limiting reactant and mole Use moles of limiting reactant and mole ratios to find moles of desired product.ratios to find moles of desired product.
5.5. Convert from moles to grams, molecules Convert from moles to grams, molecules or Liters.or Liters.
Practice Test (Ch. 9)Practice Test (Ch. 9)
1. How many moles of aluminum chloride (AlCl3) would be produced from 0.12 moles of hydrochloric acid (HCl)? Use Mole Ratio (Balanced Equation)
0.12 mol HCl = mol AlCl3mol HCl
mol AlCl3X
2
0.040
62 Al + 6 HCl 2 AlCl3 + 3 H2
0.12 mol
AlCl3mol
Practice Test (Ch. 9)Practice Test (Ch. 9)
2. If you wanted to completely react 5.0 moles of Aluminum, how many moles of hydrochloric acid (HCl) would be needed?
Use Mole Ratio (Balanced Equation)
5.0 mol Al = mol HClmol Al
mol HClX
2
15
62 Al + 6 HCl 2 AlCl3 + 3 H2
5.0 mol HClmol Al
Practice Test (Ch. 9)Practice Test (Ch. 9)
3. How many grams of hydrochloric acid would be needed to completely react 35.8 g of aluminum foil?
Convert given to moles
35.8 g Al = g HClg Al
mol AlX
2 Al + 6 HCl 2 AlCl3 + 3 H2
35.8 g Al g HCl
Use Periodic Table
1
26.98x
_________ g HCl
Units don’t match
mol Al
mol HCl
62
XUnits stilldon’t match1 mol HCl
g HCl
Use Periodic Table
36.46 Units Match= 145
Set upMole Ratio
Practice Test (Ch. 9)Practice Test (Ch. 9)
4. How many grams of aluminum would be needed to produce 67.2 dm3 of hydrogen gas?
Convert given to moles
67.2 dm3 H2 = g Aldm3 H2
mol H2x
2 Al + 6 HCl 2 AlCl3 + 3 H2
67.2 dm3 H2
g Al
1 mole = 22.4 dm3
1
22.4x
_________ g Al
Units don’t match
mol H2
mol Al
32
x Units stilldon’t match1 mol Al
g Al
Use Periodic Table
26.98 Units Match= 53.96
Set upMole Ratio
Practice Test (Ch. 9)Practice Test (Ch. 9)
5. How many molecules of carbon dioxide (CO2) would be produced by completely reacting 8.00 grams of oxygen gas (O2) with carbon monoxide (CO)? Convert given to moles
8.00 g O2 = molec.CO2g O2
mol O2x
2 CO(g) + O2 (g) 2 CO2 (g)
8.00 g O2
molec. CO2
Use Periodic Table
1
32.00x
________ molec.CO2
Units don’t match
mol O2
mol CO2
1 2
xUnits stilldon’t match1 mol CO2
molec. CO2
1 mol = 6.02 x 1023 molecules
6.02 x 1023 Units Match= 3.01 x 1023
Set upMole Ratio
Practice Test (Ch. 9)Practice Test (Ch. 9)
6. What volume in L of oxygen gas (O2) would react with 6.0 L of carbon monoxide gas (CO)?
Convert given to moles
6.0 L CO = __________ L O2L CO
mol COx
2 CO(g) + O2 (g) 2 CO2 (g)
6.0 L COL O2
1 mole = 22.4 L
1
22.4x
________ L O2
Units don’t match
mol CO
mol O2
12
xUnits stilldon’t match1 mol O2
L O2
1 mol = 22.4 L
22.4 Units Match= 3.0
Set upMole Ratio
Practice Test (Ch. 9)Practice Test (Ch. 9)
7. What volume in L of ammonia gas (NH3) would be produced from 14.0 g of nitrogen (N2) at STP?
Convert given to moles
14.0 g N2 = ________ L NH3g N2
mol N2x
N2(g) + 3 H2 (g) 2 NH3 (g)
14.0 g N2
L NH3
1 mole = Molar mass (periodic table)
1
28.0x
________ L NH3
Units don’t match
mol N2
mol NH3
1 2
xUnits stilldon’t match1 mol NH3
L NH3
1 mol = 22.4 L
22.4 Units Match= 22.4
Set upMole Ratio
Solving a Stoichiometry Solving a Stoichiometry ProblemProblem
8. If 6.0 moles of methane is mixed with 8.0 molesof O2, and the mixture is ignited, determine:
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (l)
a. The limiting reactant
Ideal situation(From Bal.Eqn.)
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (l)
Reactants
Compare the two reactants from balance equation tomoles given for each reactant in the problem.
O2CH4
=
21
Moles given inProblem
6.0 mol CH4 8.0 mol O2
O2
CH4
=
8.06.0
=1.33
1
1.33 is less than 2 so… moles O2 in given problem is the limiting reagent.
Solving a Stoichiometry Solving a Stoichiometry ProblemProblem
8. If 6.0 moles of methane is mixed with 8.0 molesof O2, and the mixture is ignited, determine:
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (l)
b. The reactant in excess
Ideal situation(From Bal.Eqn.)
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (l)
Reactants
Compare the two reactants from balance equation tomoles given for each reactant in the problem.
O2CH4
=
21
Moles given inProblem
6.0 mol CH4 8.0 mol O2
CH4
O2
=
8.06.0
= 0.75
0.75 is greater than 0.50 so… moles CH4 in given problem is the excess reagent.
= 0.50
Solving a Stoichiometry Solving a Stoichiometry ProblemProblem
8. If 6.0 moles of methane is mixed with 8.0 molesof O2, and the mixture is ignited, determine:
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (l)
c. The moles of carbon dioxide (CO2) produced.
Excess Limiting
8. If 6.0 moles of methane is mixed with 8.0 molesof O2, and the mixture is ignited, determine:
Start with the limiting reagent
8.0 mol O2 = ________ mol CO2x
c. The moles of carbon dioxide (CO2) produced.
Use Mole Ratio(Bal. Equation)
2
mol O2
mol CO2
1
4.0
Identify what you want to find
Solving a Stoichiometry Solving a Stoichiometry ProblemProblem
8. If 6.0 moles of methane is mixed with 8.0 molesof O2, and the mixture is ignited, determine:
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (l)
d. How many grams of excess reactant left over?
Excess Limiting
8. If 6.0 moles of methane is mixed with 8.0 molesof O2, and the mixture is ignited, determine:
Start with the limiting reagent
8.0 mol O2 = ________ mol CH4x
d. How many grams of excess reactant left over ?
Use Mole Ratio(Bal. Equation)
2
mol O2
mol CH4
1
4.0
Identify what you want to find1st find out how much excess gets used up.
Amount Used up
Solving a Stoichiometry Solving a Stoichiometry ProblemProblem
8. If 6.0 moles of methane is mixed with 8.0 molesof O2, and the mixture is ignited, determine:
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (l)
d. How many grams of excess reactant left over ?
Excess Limiting
d. How many grams of excess reactant left over ?
ExcessReagent
(original amount)
mol CH44.0
Amount Used up
6.0 mol CH4
- = 2.0 mol CH4
Excess molesLeft over
Solving a Stoichiometry Solving a Stoichiometry ProblemProblem
8. If 6.0 moles of methane is mixed with 8.0 molesof O2, and the mixture is ignited, determine:
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (l)
d. How many grams of excess reactant left over?
Excess Limiting
2.0 mol CH4 = ________ g CH4x
d. How many grams of excess reactant left over ?
Use molar mass(Periodic table)
1 mol CH4
g CH4 32.10
1 mole = Molar mass (Periodic table)
grams of excessreactant.
16.0532
2 sig.figs.
Solving a Stoichiometry Solving a Stoichiometry ProblemProblem
8. If 6.0 moles of methane is mixed with 8.0 molesof O2, and the mixture is ignited, determine:
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (l)
e. How many grams of water will theoretically be produced fro this reaction?
Excess Limiting
8. If 6.0 moles of methane is mixed with 8.0 molesof O2, and the mixture is ignited, determine:
Start with the limiting reagent
8.0 mol O2 = ________ g H2Ox
e. How many grams of water will theoretically be produced fro this reaction?
Use Mole Ratio(Bal. Equation)
2
mol O2
mol H2O
2
144.16
Identify what you want to find
x1 mol H2O
18.02 g H2O
Theoretical Yield
1 mole = molar mass(Periodic Table)
144.2
Solving a Stoichiometry Solving a Stoichiometry ProblemProblem
8. If 6.0 moles of methane is mixed with 8.0 molesof O2, and the mixture is ignited, determine:
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (l)
f. Determine the % yield if the actual amount of water produced during this reaction is 130.0 g.
Excess Limiting
% Yield=Theoretical Yield
Actual Yield=
144.2 g
130.0 g
from previousProblem
X 100 X 100
= 90.15%
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