1. Ideal Gas Law
PV = nRT
P= pressure (atm)
V= volume (L)
n= Mole Gas (mol)
T= temperature (K) R= universal gas constant
Ex: H2 has a volume of 8.56 L at 0oC and 1.5 atm. Calculate the moles of H2 present.
R = L* atm mol * K
Given
V= 8.56 L
T = 0oC = 273 K
P = 1.5 atm
n = ?
R = atm L/mol K
n = PV RT
____
n = (1.5 atm)(8.56 L)
_______________________
( atm L/mol K)(273 K)
n = 0.57 mol

2. Learning Check Ideal Gas Law formula: Unit for P: Unit for V:
Unit for n:
Value & unit of R:
Unit for T:

3. Dalton’s Law of Partial Pressures
Partial Pressure – pressure that a gas would exert if it alone in the container.
Ptotal = P1 + P2 + P3…
Ex: A container holds three gases: oxygen, carbon dioxide, and helium. The partial pressures of the three gases are 2.00 atm, 3.00 atm, and 4.00 atm, respectively. What is the total pressure inside the container?
Given
P1= 2.00 atm
P2= 3.00 atm
P3= 4.00 atm
Ptotal= ?
Ptotal = P1 + P2 + P3
Ptotal = 2.00 atm atm atm
Ptotal = 9.00 atm

4. A common method of collecting gas samples in the laboratory is to bubble the gas into a bottle filled with water and allow it to displace the water. When this technique is used, however, the gas collected in the bottle contains a small but significant amount of water vapor. As a result, the pressure of the gas that has displaced the liquid water is the sum of the pressure of the gas plus the vapor pressure of water at that temperature. The vapor pressures of water at various temperatures are given in Table.
PTotal - Pvapor = PGas

5. Ex: A student collects oxygen gas by water displacement at a temperature of 16°C. The total volume is 188 mL at a pressure of 92.3 kPa. What is the pressure of oxygen collected?
Given
T = 16°C
Pvapor =
V = 188 mL (doesn’t matter)
Ptotal = 92.3 kPa
Pgas= ?
PTotal - Pvapor = PGas
1.82 kPa
92.3 kPa – 1.82 kPa = PGas
Pgas = 90.5 kPa

6. Ex: Hydrogen gas is collected by water displacement
Ex: Hydrogen gas is collected by water displacement. Total volume collected is L at a temperature of 17°C and a pressure of atm. What is the pressure of dry hydrogen gas collected? How many moles of hydrogen are present?
PTotal - Pvapor = PGas
Given
T = 17°C = 290. K
Pvapor =
V = L
Ptotal = atm
Pgas= ?
ngas =
99.7 kPa – 1.94 kPa = PGas
1.94 kPa
Pgas = 97.8 kPa
x ________
kPa
atm
101.3 1 =
0.965 atm
atm
kPa 1
101.3
x ________ =
99.7 kPa
n = (0.965 atm)(0.461 L)
_______________________
( atm L/mol K)(290. K)
n = PV RT
____
n = mol

7. Learning Check Dalton’s Law formula:
In a sentence summarize how Dalton’s Law works.
What does it mean to collect gas over water?

8. Gas Stoichiometry or use PV = nRT
STP = Standard Temperature and Pressure
Standard Temperature = 0oC
Standard Pressure = 1 atm
Molar Volume molgas = 22.4 Lgas
Ex 1: A sample of N2 has a volume of 1.75 L at STP. How many moles of N2 are present? 1
mol
1.75 L
x ________ =
mol
22.4 L or
use PV = nRT

9. Ex 2: Calculate the volume of O2 produced at 1
Ex 2: Calculate the volume of O2 produced at 1.00 atm and 25 oC by the decomposition of 10.5g KClO3.
2KClO3  2KCl + 3O2
V = nRT P
____
Given
V= ?
T = 25oC = 298 K
P = 1.00 atm
R = atm L/mol K
n = 10.5 g KClO3
V = (0.128 mol) ( atm L/mol K)(298 K)
_______________________________
1.00 atm 1
mol KClO3 3
mol O2
x ___________
x __________ =
0.128 mol
122.6
g KClO3 2
mol KClO3
V = 3.13 L

10. Ex 3: Calculate the volume of CO2 produced at STP from 152g of CaCO3.
CaCO3  CaO + CO2
152 g CaCO3 1
mol CaCO3 1
mol CO2
22.4 L
x ___________
x __________
x _______ =
100.1
g CaCO3 1
mol CaCO3 1
mol
34.0 L or
use PV = nRT

11. Learning Check What does STP mean? STP Temperature = STP Pressure =
STP Temperature =
STP Pressure =
1 mole of gas = ______ L of gas