Chapter 7

Overhead Kinetic Theory of gasses.

Four terms to describe a Gas

1. Pressure- (P) kinetic energy of gas particles resulting in a force.

Pressure = force/area = units 1 atm = mmHg = 760 torr = 760 barr

2. Volume- (V) volume of the container is equal to the volume of the gas.

units = liters (L)

3. Temperature-(T) average kinetic energy of gas particles.

units = always in Kelvin

K = ° C + 273

4. Amount of gas-(n)

units = moles

Gas Pressure-

    1. Atmospheric pressure- column of air directly above your head, gravity provides the force.

      2. Barometer-

       

       

       

      Diving-

       

    2. Vapor pressure- particles escape, have energy and exert a force in a closed container called a vapor pressure. Dependent on substance, and temp.

      3.  

    3. Boiling point- When vapor pressure equals atmospheric pressure.

      4. Water boils at 1 atm, 100° C.

       

      If you are camping in Nepal will it take longer or shorter to cook your stew?

      Can you hat water past 100° C?

      2. Deriving the ideal gas law.

      A x B = 1 inverse relationship A increases B decreases

      A = B direct relationship A increases B increases

      a) P, V

      b) V, n (moles)

       

       

      c) V, T

       

    4. Put them all together

      5. PV = nRT ideal gas law

    5. Solve for R

      6. R = PV/nT = (1.00 atm)(22.4 L)/ (1 mole)(273 K) =

       

    6. examples:

ex. 7-1. A diver�s lungs have a volume of 2.0 L. If the diver is at 99 feet and holds their breath to the surface, what is the new volume of their lungs?

 

 

 

 

 

ex 7-2. What is the final volume when a 3.4 L tire is heated from 23.0° C to 40.0° C.

 

 

ex 7-3. A air tank increases in pressure from 2.0 atm to 4.0 atm. If the original temp was 23.0° C, what must be the final temp?

 

 

 

 

 

ex 7-4. A 25.0 mL ballon is released underwater (99 ft, 4 atm) at 11° C and rises to the surface. If the surface temp is 18° C what is the new volume.

 

 

 

 

One set of conditions.

ex 7-5. How many moles of a gas occupy a 13.5 L flask at 24.5° C and 897 torr?

 

 

 

 

 

ex 7-6. What temp is 2.4 g of nitrogen gas contained in a 2.2 L flask at 1.3 atm?

 

 

 

 

3. STP Conditions (standard temperature and pressure)

Temp = 273 K, 0° C Pressure = 1 atm

Molar Volume of a gas at STP,

PV = nRT V = nRT/P = (1.0 mole)(0.0821 L atm/mol K)(273 K)/ 1 atm = 22.4 L

1 mole = 22.4 L any gas

 

ex. 7-7. What is the volume of 22.3 g of bromine gas at STP?

 

 

 

4. Partial Pressures � Total pressure of a mixture of gasses is equal to the total of their partial pressures. Not gas dependent.

Pt = P1 + P2 + P3 + P4 ......

ex. 7-8. Nitrogen gas is collected over water at 17 ° C in a 4.0 L flask. The total pressure inside the flask is 1.24 atm and the vapor pressure of water at this temp is 14.5 torr. What is the pressure of the nitrogen gas?

 

 

5. Gas Dissolved in a Liquid � Henry�s Law- amount of gas that dissolves in a liquid at a given temp is related to the pressure of that gas above that liquid.

Dependent of temp and pressure.

decompression chamber.

How do lungs work.