Gases 2015.notebook
October 27, 2015
Gas Laws
Gas external
internal
temperature
T
always K
ideal
pressure P
in atm or mmHg
amount of volume
non ideal
gas particles
particles
­travel fast
in moles
­very far apart
n
­collisions are elastic in reality
­no attractions or
not all gases are
"perfect"
repulsions in L V
in mL
n=no. of moles
good estimation
PV=nRT
Ideal Gas
Law
(
( )
) P + an2 V­nb = nRT
v2 where a = Pv2
n
v=4/3 r3 b=4(4/3 ( 2 )3 N
S
KE
YI
accounts for Coulomb's Law
elastic collisions
http://sci­culture.com/advancedpoll/GCSE/collisions.htm
force collisions = area
pressure =
= area
Mar 14­8:15 AM
1
Gases 2015.notebook
October 27, 2015
Gas­­ external factors force collisions = area
Pressure = area
Temperature = speed of particles
Volume
no. of particles (moles)
rigid container
flexible container
Volume­constant
Pressure is constant
n ­ Mass/moles­constant
n ­Mass/moles­constant
Pin =Pout
if T
then P if T
then V if T
then P P1 = P2
V1 = V2
T1 T2
T1 T2
T, collisions (P)
area
if T
then V T, collisions , V (P)
area
both are linear relationships
Mar 14­12:06 PM
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Gases 2015.notebook
October 27, 2015
Temperature constant
n ­Mass/moles­constant
use a piston to demonstrate:
if V
then P if V (more collisions)
then P P1V1 = P2V2
reciprocal relationship
Put all 3 together:
Guy­Lussacs Law
P1 = P2
Charles Law
V1 = V2
T1 T2
T1 T2
Boyles Law
P1V1 = P2V2
Combined Gas Law
V1P1 = V2P2
6 variables: solve for one
T1 T2
Temperature must be in Kelvin for all gas laws
o
C + 273 = K
Convert 25oC to K Convert 300K to oC Mar 14­12:29 PM
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Gases 2015.notebook
October 27, 2015
A gas had an initial pressure of 2.4 atm and a volume of 5.6 L. If the pressure of the gas changes to 1.7 atm, what is the new volume?
Held constant:
Variables:
Plug into equation:
Mar 14­1:52 PM
4
Gases 2015.notebook
October 27, 2015
A balloon has a volume of 3.4 L at 213 K. If the temperature drops to 197 K, what is the volume of the balloon?
Held constant:
Variables:
Plug into equation:
A balloon has a volume of 1.2 L at a temperature of 253 K. The temperature changes to 305 K. What is the new volume of the balloon?
Mar 14­1:55 PM
5
Gases 2015.notebook
October 27, 2015
The pressure inside a container is 770 mm Hg at a temp of 57 degrees Celsius. What would the pressure be at 75 degrees Celsius?
A gas filled balloon has a temp of 42 degrees C at a pressure of 0.75 atm. The pressure changes to 1.02 atm. What is the new temperature of the gas in the balloon?
Mar 14­1:57 PM
6