PERFORMANCE OBJECTIVES

1
PERFORMANCE OBJECTIVES

• Predict, write, and balance chemical equations
• Recognize types of reactions
• Use the Kinetic Molecular Theory explain the
  relationship between pressure, volume,
  temperature, and number of particles in a gas
  sample.

2

• Explain the relationship between temperature and
  average kinetic energy.
• Perform calculations using the ideal gas law.
• Interpret Daltons Law of Partial Pressures and
  use it to calculate partial pressures and total
  pressures.

3

• Solve gas law problems concerning changes in gas
  pressure, volume, or temperature.
• Calculate mass-volume, volumevolume and limiting
  reactant problems for chemical reactions
• Calculate percent yield

4
GASES
5
KINETIC THEORY OF MATTER

• Particles are in constant random motion.
• These particles are elements.
• Collisions are perfectly elastic - no loss of
  energy.

6
PRESSURE

• Due to the collisions of air molecules with each
  other and the surfaces of the container
• and number of collisions
• At 25 degrees Celsius, the average speed of
  oxygen is 443 m/s.
• 4 1/2 billion collisions per second

7
PRESSURE CONTINUED

• of collisions depend upon
• temperature
• of particles
• mass of particles
• barometer

8
Pressure continued

• Speed of gas particles depends upon temperature
  and mass of particles
• Kinetic energy
• temperature

9
TEMPERATURE

• Kelvin
• formula
• practice conversions
• standard temperature

10
STANDARD PRESSURE

• Average pressure at sea level

11
UNITS OF PRESSURE

• mmHg
• kPa
• atm
• torr
• psi

12
STP

• Temperature and pressure where gases behave most
  ideally
• ideal gas

13
CHARLES LAW

• Statement of law
• Formula
• A 225 cm3volume of gas is collected at 58
  degrees Celsius. What volume would this sample
  of gas occupy at standard temperature? Assume a
  constant pressure.

14
BOYLES LAW

• Statement of law
• formula
• A gas is collected in a 242 cm3 container. The
  pressure of the gas in the container is measured
  and determined to be 87.6 kPa What is the volume
  of this gas at standard atmospheric pressure?
  Assume that the temperature remains constant.

15
DALTONS LAW

• Statement of the law
• In a gas mixture, each type of gas exerts
  pressure that contributes to the total pressure.
  Each gas acts alone.
• Gas collected by bubbling it through water
• gas must be insoluble in water
• water vapor is collected with gas
• must remove pressure exerted by water

16
SAMPLE PROBLEM

• A quantity of gas is collected over water at 8
  degrees Celsius in a 353 cm3 container. The
  manometer indicates a pressure of 84.5 kPa. What
  volume would the dry gas occupy at standard
  atmospheric pressure and 8 degrees Celsius?

17
COMBINED GAS LAW

• Calculations involving situations in which both
  the temperature and pressure varies.
• Formula
• The volume of a gas measured at 75.6 kPa pressure
  and 60.0 degrees Celsius is to be corrected to
  correspond to the volume it would occupy at STP.
  The measure volume of the gas is 10.0 cm3.

18
DIFFUSION OF GASES

• Varies according to
• speed of molecules
• smaller masses diffuse faster
• used to separate gases from each other
• Grahams Law
• Formula

19
SAMPLE PROBLEM

• Find the relative diffusion for the gases krypton
  and bromine.

20
AVOGADROS PRINCIPLE

• At equal temperatures and pressures, equal
  volumes of gases contain the same number of
  molecules.
• This allows us to calculate the molar volume of a
  gas,
• Molar volume - volume occupied of by 1 mole of
  any gas under standard conditions.
• 22.4 dm3

21
IDEAL GAS LAW

• Allows one to combine all 4 variables concerned
  with the physical characteristics of gases
• temperature
• volume
• pressure
• number of particles

22
FORMULA

• PV nRt
• n number of moles
• R a constant
• Values for R
• 8.31 dm3skPa/molsK
• 0.0821 litersatm/molsK

23
SAMPLE PROBLEMS

• What pressure is exerted by 4.50 moles of gas in
  a 198 dm3 container at a temperature of 8 degrees
  Celsius?
• What volume would be occupied by 3.22 moles of
  gas at a temperature of 35 degrees Celsius and a
  pressure of 93.2 kPa?

24
SAMPLE PROBLEMS CONTINUED

• How many moles of gas can be contained in a 1.44
  dm3 container at a temperature of 32 degrees
  Celsius and 93.5 kPa?
• What temperature in degrees Celsius is a gas if
  2.31 moles of it in a occupy 61dm3 container at
  94.6 kPa?

25
MOLECULAR MASS/WEIGHT

• Use Ideal Gas Law to determine the molecular mass
  of a gas from laboratory measurements.
• Useful in identifying an unknown gas.
• Formula
• apply formula to ideal gas law

26
SAMPLE PROBLEM

• Suppose we measured the mass of the vapor of an
  unknown compound contained in a 273 cm3 gas bulb.
  We find that the bulb contains 0.750 grams of
  gas at 97.2 kPa pressure and 61 degrees Celsius.
  What is the molecular mass of the gas?

27
GAS STOICHIOMETRY

• What volume of hydrogen at STP can be produced
  when 6.54 grams of zinc react with hydrochloric
  acid?

28
GAS LIMITING AND EXCESS

• How many grams of carbon dioxide are formed of
  10.0 grams of carbon are burned in 20.0 dm3 of
  oxygen. Assume STP.

29
Gay-Lussacs Law

• Statement of the law
• Formula
• Sample problem The gas in an aerosol can is at
  a pressure of 3 atms at 25oC. Directions on the
  can warn the user not to keep the can in a place
  where the temperature exceeds 52oC. What would
  the gas pressure in the can be at 52oC?