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GAS LAWS


I. Variables used to Measure Gas samples


A. _________________: amount of ______________ it takes up

                    units: _________ or ________

B. ______________: how much is there?

            1.       _____________ in grams (m)
        *  2.      __________________  (new symbol, ______)
            3.      ________________  or  _______________

C. _____________________

Three temperature scales:
__________________, K
__________________, oC
__________________, oF


K = oC + 273

oF = 1.8 oC + 32

oC = (oF - 32) / 1.8



D. ____________________: amount of _____________ per unit ______________

units: 

___________ = pounds / square inch
___________ = atmospheres
___________ = millimeters of mercury
___________ = inches of mercury                                                                                                                                                                          ___________ = centimeters of water                                                                                                                                                                           ___________ = torricelli
___________ = kiloPascals

conversions:

14.7 lbs/in2 = 1 atm = 760 mm Hg = 760 torr = 101.3 kPa

Examples:

Convert:

1. 250 mL to L


2. 6.2 L to mL


3. 42 g N2 to molecules N2


4. 3 mol oxygen to grams


5. 70 oF to oC

6. 15 oC to oF


7. 25 oC to K


8. 300 K to oC


E. Standard Conditions

___________ = ______________________________________ = __________ and _________

 

 


II. Kinetic Molecular Theory of Gases (or if you could see the gas particles in the air, what would they be doing?)


A. Gases consist of tiny particles with practically no volume. They are tiny, tiny pinpoints, taking up essentially no space.

Evidence:

1. ___________________________________________________________

2. ___________________________________________________________

3. ____________________________________________________________


B. The gas particles zip around in rapid straight line motion. They never curve. Remember, particles in a solid vibrate and particles in a liquid roll and slide over each other.

Evidence:

1. _____________________________________________________________

2. _____________________________________________________________

3. _____________________________________________________________


C. The particles lose no energy due to collisions. They don’t “tire” out”, like a bouncing ball; they keep moving.

Evidence:

__________________________________________________________________ 
__________________________________________________________________


D. The average kinetic energy is directly related to temperature.
The higher the temperature, the more energy the particles have. There is, however, a distribution of energy within a sample.

Evidence:

 

E. There are no attractive or repulsive forces between gas particle. As they pass each other, they don’t attract or repel each other. At low temperatures and/or high pressures, this is not true; they will attract.

Evidence:

1. ___________________________________________________

2. ___________________________________________________



REVIEW: Explanation of Phenomena involving GAS

1. Why do gases exert pressure?

Gas particles are constantly colliding with the inside of its container.
 This causes a _________________ on the 
______________ of the surface. 

Pressure is force per unit area  or   P =   _________________



(tire or balloon)


2. Evaporation

EVAPORATION is LIQUID --------------> GAS (at any temperature)


Particle X gets hit and is popped out of
the liquid. ONLY HIGH ENERGY LIQUID
PARTICLES CAN DO THIS AND THEY
MUST BE AT THE SURFACE.


(liquid particles sliding and vibrating)


Why does perspiring cool us off? 

Which evaporates faster, a rain puddle on a cold day or one on a hot day?


3.  Boiling

________________ is a special case of LIQUID -->  GAS

 



4. Sublimation

SUBLIMATION IS SOLID ------------> GAS (without melting)

                                                                  Particles X gets vibrated
                                                                  against, becomes a high
                                                                  energy solid particle and is
                                                                  ejected from the solid

(vibrating solid particles)


5. Condensation (or Deposition)

GAS ---------------------> LIQUID (OR SOLID)

                    

                             -------->                       --------->

gas particles               gas particles attracting                 solid or liquid

 

Ideal Gases vs. Real Gases

 

 

 

 







III. Equation of State for an Ideal Gas: Ideal Gas Law

 

                             H2                                        O2


                     P = 2 atm                       P = 4 atm
                     V = 0.5 L                      V = 2 L
                     T = 300 K                     T = 150 K
                     n = 0.04065 mol            n = 0.650 mol


A little trial and error produces:




To use this equation, P must be in ___________ V in ___________, n is ________, T is _______

The ideal gas law is :


R = ____________________




Examples:

1) What volume will 8 moles of hydrogen gas occupy at 2 atm and 81 oC?







2) A sample of gas is collected in a 3 L flask at 780 torr and 22 oC. How many moles of gas are present?

 

 

3) What must be the temperature (in oC) for 2 moles of gas in an 11.2 L flask to exert a pressure of 1 atm?






4) What volume will 10 moles of gas occupy at STP?






Variations of the Ideal Gas Law:


moles =                             or                  n =


so:

P V = 



1) What is the mass of 1 L of hydrogen at STP?






2) Find the molecular weight of a gas if 0.20 g of it occupies 100 mL at 0.5 atm and 0 oC?





3) What is the temperature (in K and oC) if 21.3 g Cl2 occupies 60 L at 4 atm?

 

 

4) Find the molecular weight of a gas that occupies 1 L at 27 oC and 720 torr?










IV. Combined Gas Law

What happens to a gas when the conditions change:






















V. Boyle’s Law















VI. Charles’ Law


















VII. Gay-Lussac’s Law







 

 

 

 

VIII. Dalton’s Law of Partial Pressure



 

 

 

 

 

 

HOMEPAGE