Chapter 11
Section 8
The Ideal Gas Law
Ideal Gas Law
• We know that the volume of a gas varies
directly with the Kelvin temperature and
inversely with the pressure. We also know
from Avogadro that volume varies directly
with the number of moles of gas.
• Put it all together and we get the ideal gas
law:
PV = nRT
PV = nRT
• Where:
P = pressure
V = volume
T = temperature
n = number of moles
R = the ideal gas constant, which varies in
value depending on what units pressure is
measured in
Ideal Gas Constant, R
R = 0.0821 L•atm /mol•K
= 8.31 L•KPa / mol•K
= 62.4 L•torr / mol•K
This is a second road on the mole map between
moles and volume when conditions are NOT
at STP!!!!
Sample problem 1
• What is the pressure in atmosphere exerted
by a 0.500 mol sample of nitrogen gas in a
10.0 L container at 298K?
Sample problem 1
• What is the pressure in atmosphere exerted
by a 0.500 mol sample of nitrogen gas in a
10.0 L container at 298K?
• solution:
solve PV = nRT for P
Sample problem 1
• What is the pressure in atmosphere exerted
by a 0.500 mol sample of nitrogen gas in a
10.0 L container at 298K?
• solution:
solve PV = nRT for P
P = nRT =
V
Sample problem 1
• What is the pressure in atmosphere exerted
by a 0.500 mol sample of nitrogen gas in a
10.0 L container at 298K?
• solution:
solve PV = nRT for P
P = nRT = (0.500 mol)(0.0821 Latm/molK)(298 K)
V
10.0L
Sample problem 1
• What is the pressure in atmosphere exerted
by a 0.500 mol sample of nitrogen gas in a
10.0 L container at 298K?
• solution:
solve PV = nRT for P
P = nRT = (0.500 mol)(0.0821 Latm/molK)(298 K)
V
10.0L
= 1.22 atm
Sample problem 2
• What mass of chlorine gas, Cl2, in grams, is
contained in a 10.0 L tank at 27°C and 3.50
atm of pressure?
• Solution:
Sample problem 2
• What mass of chlorine gas, Cl2, in grams, is
contained in a 10.0 L tank at 27°C and 3.50
atm of pressure?
• Solution:
1. solve PV = nRT for n moles
2. convert moles of Cl2 to grams
Sample problem 2
• What mass of chlorine gas, Cl2, in grams, is
contained in a 10.0 L tank at 27°C and 3.50
atm of pressure?
• Solution:
1. solve PV = nRT for n moles
n = PV
RT
Sample problem 2
• What mass of chlorine gas, Cl2, in grams, is
contained in a 10.0 L tank at 27°C and 3.50
atm of pressure?
• Solution:
1. solve PV = nRT for n moles
n = PV = (3.50atm)(10.0L)
RT (0.0821 Latm/molK)(300K)
Sample problem 2
• What mass of chlorine gas, Cl2, in grams, is
contained in a 10.0 L tank at 27°C and 3.50
atm of pressure?
• Solution:
1. solve PV = nRT for n moles
n = PV = (3.50atm)(10.0L)
RT (0.0821 Latm/molK)(300K)
= 1.42 mol Cl2
Sample problem 2
• What mass of chlorine gas, Cl2, in grams, is
contained in a 10.0 L tank at 27°C and 3.50
atm of pressure?
• Solution:
2. convert moles of Cl2 to grams
Sample problem 2
• What mass of chlorine gas, Cl2, in grams, is
contained in a 10.0 L tank at 27°C and 3.50
atm of pressure?
• Solution:
2. convert moles of Cl2 to grams
1.42 mol Cl2 x 70.90 g
1 mol
Sample problem 2
• What mass of chlorine gas, Cl2, in grams, is
contained in a 10.0 L tank at 27°C and 3.50
atm of pressure?
• Solution:
2. convert moles of Cl2 to grams
1.42 mol Cl2 x 70.90 g
1 mol
= 101g Cl2
Homework
• Read pages 379-385
• Answer questions 402 #60, 62, 64, 68, & 70