1. Bellwork:
What is the volume, in liters, of mol of oxygen gas at 20.0ºC and atm pressure?
V = ?
n = mol
T = 20ºC = 293 K
P = atm
PV = nRT
6.17 L O2
nRT P
0.250 mol (.0821 L·atm/mol·K) (293 K)
0.947 atm = V = =

2. Gas Stoichiometry at Non-STP Conditions

3. OBJECTIVES
Use a chemical equation to specify volume ratios for gaseous reactants or products, or both.
Use volume ratios and the gas laws to calculate volumes, masses, or molar amounts of gaseous reactants or products.

4. Gas Stoichiometry 2Na(s) + Cl2 (g) → 2NaCl (s) AT STP: Non-STP
If I have 50.0 L of chlorine gas, how many moles of sodium chloride can be made…
AT STP:
use 22.4 L/mol to find moles of gas
Then use mole ratio
Non-STP
start with ideal gas law to convert liters to moles of gas (PV = nRT)

5. If given L of gas and are looking for L of a different gas, just use the mole ratio!
For example:
N2(g) + 3 H2(g) → 2 NH3(g)
How many liters of NH3 can be produced from 5.5 L of H2 gas at 298 K and 0.97 atm?
3.67 L

6. Gas Stoichiometry Problem
What volume of CO2 forms from 5.25 g of CaCO3 at 103 kPa & 25ºC?
CaCO3 (s)  CaO (s) + CO2 (g)
5.25 g
? L non-STP
Always start by converting your given into moles!! Then find moles of CO2.
5.25 g
CaCO3
1 mol
CaCO3
100.09g
1 mol
CO2
CaCO3
= mol CO2
Plug this into the Ideal Gas Law to find liters.

7. Gas Stoichiometry Problem
What volume of CO2 forms from g of CaCO3 at 103 kPa & 25ºC?
GIVEN:
P = 103 kPa
V = ?
n = mol
T = 25°C = 298 K
R = LkPa/molK
WORK:
PV = nRT V = nRT/P
V=(0.0525mol)(8.315LkPa/molK)(298K)
(103 kPa)
V = 1.26 L CO2

8. Gas Stoichiometry Problem
How many grams of Al2O3 are formed from L of O2 at 97.3 kPa & 21°C?
4 Al O2  2 Al2O3
15.0 L
non-STP
? g
GIVEN:
P = 97.3 kPa
V = 15.0 L
n = ?
T = 21°C = 294 K
R = LkPa/molK
WORK:
PV = nRT
n = PV/RT
n= (97.3 kPa) (15.0 L) (8.315LkPa/molK) (294K)
n = mol O2
Given liters: Start with Ideal Gas Law and calculate moles of O2.
NEXT 

9. Gas Stoichiometry Problem
How many grams of Al2O3 are formed from 15.0 L of O2 at 97.3 kPa & 21°C?
4 Al O2  2 Al2O3
15.0L
non-STP
? g
Use stoich to convert moles of O2 to grams Al2O3.
0.597
mol O2
2 mol Al2O3
3 mol O2
g Al2O3
1 mol
Al2O3
= 40.6 g Al2O3

10. CaCO3(s) CaO(s) + CO2(g)
? g
5.00 L
How many grams of calcium carbonate must be decomposed to produce 5.00 L of carbon dioxide gas at STP?
V = 5.00 L
T = 0ºC = 273 K
P = 1 atm
n = ?
At STP
1 mole = 22.4 L
5.00 L n
1 mol
22.4 L
.223 mol CO2 = x =
1 mol CaCO3
1 mol CO2
g CaCO3
1 mol CaCO3
22.3 g CaCO3
.223 mol CO3 = x x

11. WO3(s) + 3H2(g) W(s) + 3H2O(g)
? L
How many liters of hydrogen gas at 35ºC and atm are needed to react completely with 875 g of tungsten oxide?
1 mol WO3
g WO3
3 mol H2
1 mol WO3
11.3 mol H2 =
875 g WO3 x x
n = mol
P = atm
T = 35ºC = 308 K
V = ?
PV = nRT
nRT P
11.3 mol (.0821 L·atm/mol·K) (308 K)
(0.980 atm) V =
292 L H2 = =