1.use the ideal gas law to solve a gas stoichiometry problem
TRANSCRIPT
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Gas Laws: GasStoichiometry
At the conclusion of our time together, you should be able to:
1. Use the Ideal Gas Law to solve a gas stoichiometry problem.
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Gases and Stoichiometry
2 H2O2 (l) ---> 2 H2O (g) + O2 (g)
Decompose 1.1 g of H2O2 in a flask with a volume of 2.50 L. What is the volume of O2 at STP?
Bombardier beetle uses decomposition of hydrogen peroxide to defend itself.
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Gases and Stoichiometry
2 H2O2 (l) ---> 2 H2O (g) + O2 (g)
Decompose 1.1 g of H2O2 in a flask with a volume of 2.50 L. What is the volume of O2 at STP?
Solution1.1 g H2O2 1 mol H2O2 1 mol O2 22.4 L
O2
34 g H2O2 2 mol H2O2 1 mol O2
= 0.36 L O2 at STP
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Gas Stoichiometry: Practice!
How many grams of He are present in 8.0 L of gas at STP?
= 1.4 g He
8.0 L He x 1 mol He
22.4 L He
x 4.00 g He
1 mol He
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Gas Stoichiometry Trick
If reactants and products are at the same conditions of temperature and pressure, then mole ratios of gases are also volume ratios.
3 H2(g) + N2(g) 2NH3(g)
3 moles H2 + 1 mole N2 2 moles NH3 67.2 liters H2 + 22.4 liter N2 44.8 liters NH3
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Gas Stoichiometry Trick Example
How many liters of ammonia can be produced when 12 liters of hydrogen react with an excess of nitrogen in a closed container at constant temperature?
3 H2(g) + N2(g) 2NH3(g)
12 L H2
L H2
= L NH3 L NH3
3
28.0
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What if the problem is NOT at STP?
1. You will need to use PV = nRT
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Gas Stoichiometry Example on HO
How many liters of oxygen gas, at 1.00 atm and 25 oC, can be collected from the complete decomposition of 10.5 grams of potassium chlorate?
2 KClO3(s) 2 KCl(s) + 3 O2(g)
10.5 g KClO3 1 mol KClO3
122.55 g KClO3
3 mol O2
2 mol KClO3
0.13 mol O2
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Gas Stoichiometry Example on HO
How many liters of oxygen gas, at 1.00 atm and 25 oC, can be collected from the complete decomposition of 10.5 grams of potassium chlorate?
2 KClO3(s) 2 KCl(s) + 3 O2(g)
3.2 L O2
(1.0 atm)(V) (0.08206 atm*L/mol*K) (298 K)(0.13 mol)
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Gas Laws: Dalton, Density and Gas Stoichiometry
At the conclusion of our time together, you should be able
to:
1. Explain Dalton’s Law and use it to solve a problem.
2. Use the Ideal Gas Law to solve a gas density problem.
3. Use the Ideal Gas Law to solve a gas stoichiometry problem.
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GAS DENSITYGAS DENSITY
High density
Lower density
22.4 L of ANY gas AT STP = 1 mole
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Gas Density
molar mass
molar volume
massDensity
volume
… so at STP…
molar mass
22.4 LDensity
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Density and the Ideal Gas Law
Combining the formula for density with the Ideal Gas law, substituting and rearranging algebraically:
MPD
RT
M = Molar Mass
P = Pressure
R = Gas Constant
T = Temperature in Kelvins
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Gas Stoichiometry #4
nRT
VP
How many liters of oxygen gas, at 37.0C and 0.930 atmospheres, can be collected from the complete decomposition of 50.0 grams of potassium chlorate?
2 KClO3(s) 2 KCl(s) + 3 O2(g)
= “n” mol O2
50.0 g KClO3 1 mol KClO3
122.55 g KClO3
3 mol O2
2 mol KClO3 = 0.612 mol O2
L atm(0.612mol)(0.0821 )(310K)
mol K0.930atm
= 16.7 L
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Try this one!
How many L of O2 are needed to react 28.0 g NH3 at 24°C and 0.950 atm?
4 NH3(g) + 5 O2(g) 4 NO(g) + 6 H2O(g)