IDEAL GAS LAW

1
IDEAL GAS LAW

• Be consistent with units!
• This law was derived by combining Boyles Law,
  Avogadros Law, and Charles Law into one formula.

2
EXAMPLE PROBLEM

• Calculate the temperature of 7.5 g H2 gas if the
  volume is 52.5 L and the pressure is 620 Torr.

3
Daltons Law of Partial Pressure

• Daltons Law of Partial Pressure states that the
  total pressure of a mixture of gases is equal to
  the sum of the partial pressures of the gases
• PT P1 P2 P3

4
Gases are often collected over water

• Daltons Law of Partial Pressure is often used to
  correct for the vapor pressure of water, which is
  a function of temperature but not volume or
  amount. The vapor pressure of water can be
  looked up in standard reference books such as the
  Handbook of Chemistry and Physics.

5
Vapor Pressure Problem

• A gas is collected over water at 300K (27oC), at
  1.00 atm(760 Torr). Calculate the pressure of the
  dry gas.
• PT Pgas Pwater
• Pgas PT - Pwater
• At 27oC, the vapor pressure of water is 26.74
  Torr
• The pressure of dry gas is Pgas760-26.74733 Torr

6
EXAMPLE PROBLEM

• 3O2 2O3
• How many L of O3 can be formed from 64 g of O2
  at STP?
• MM(O2) 2 x 16 32g/mol
• mol O2 g/MM 64/32 2.0 mol
• mol O3 2 mol O2 x (2O3/3O2) 1.33 mol
• PVnRT VnRT/P (1.33)(.082)(273)/1
• V29.8 L

7
3O2 2O3

• How many L of O3 can be formed from 2 moles of
  O2 at STP?

8
Putting it all together

• Stoichiometric conversion problem