Not
long
ago, in a chemistry
Mayso
the
FORCE/area
be with you
lab far far away…
1. Describe Gay-Lussac’s Law with a formula
2. Use Gay-Lussac’s Law to determine either
a temperature or volume
3. Combine all three laws into the Combined
Gas Law
4. Use the Combined Gas Law to determine
either temperature, volume or pressure
If n and V are
constant,
then P α T
P and T are directly
proportional.
P1 P2

T1 T2

If one temperature
goes up, the
pressure goes up!
Joseph Louis GayLussac (1778-1850)
Gay Lussac’s Law Summary
The pressure and temperature of a gas are
directly related, provided that the volume
remains constant.
P1 P2

T1 T2
P1
P2
T1
T2
3.00 atm
298 K
P2
325 K
3.3 atm
P1
P2
T1
T2
1.8 atm
1.9 atm
293 K
T2
310 K or
36 oC
Now let’s put all 3 laws
together into one big
law…….

The good news is that you don’t
have to remember all three gas
laws! Since they are all related
to each other, we can combine
them into a single equation. BE
SURE YOU KNOW THIS EQUATION!
PV
PV
1 1
2 2

T1
T2
No, it’s not related to R2D2
The Combined Gas Law
The combined gas law expresses the
relationship between pressure, volume and
temperature of a fixed amount of gas.
PV
PV
1 1
2 2

T1
T2
Boyle’s law, Gay-Lussac’s law, and Charles’
law are all derived from this by holding a
variable constant.
If you should only need one of the other
gas laws, you can cover up the item that
is constant and you will get that gas law!
P1 V1
T1
=
P2 V2
T2
Boyle’s Law
Charles’ Law
Gay-Lussac’s
Law
Greatest Reasons for Termination
from a Job
1.
The inability to get along with co-workers and
supervisors.
2.
Absenteeism
3.
Lack of interest
4.
Continuously making costly mistakes
5.
Does not follow directions
6.
Shows an unwillingness to learn
A sample of helium gas has a volume of 0.180
L, a pressure of 0.800 atm and a temperature
of 29°C. What is the new temperature(°C) of
the gas at a volume of 90.0 mL and a pressure
of 3.20 atm?
Set up Data Table
P1 = 0.800 atm
V1 = 180 mL
T1 = 302 K
P2 = 3.20 atm
V2 = 90 mL
T2 = ??
P1 = 0.800 atm
V1 = 180 mL
T1 = 302 K
P2 = 3.20 atm
V2 = 90 mL
T2 = ??
P1 V 1
T1
=
P2 V 2
T2
P1 V1 T2 = P2 V2 T1
T2 = 3.20 atm x 90.0 mL x 302 K
0.800 atm x 180.0 mL
= 604 K
T2 = 604 K - 273 = 331 °C
Hint #5. A record of data is essential. It
fools the instructor into thinking that you
were working.
1. Describe Gay-Lussac’s Law with a formula.
2. Use Gay-Lussac’s Law to determine either
a temperature or volume
3. Combine all three laws into the Combined
Gas Law
4. Use the Combined Gas Law to determine
either temperature, volume or pressure
A gas has a volume of 675 mL at 35°C and
0.850 atm pressure. What is the temperature
in °C when the gas has a volume of 0.315 L
and a pressure of 802 mm Hg?
P1 = 0.850 atm
V1 = 675 mL
T1 = 308 K
P2 = 1.06 atm
V2 = 315 mL
T2 = ??
P1 V 1
T1
=
P2 V 2
T2
P1 V1 T2 = P2 V2 T1
T2 = 1.06 atm x 315 mL x 308 K
= 179 K
0.850 atm x 675 mL
T2 = 179 K - 273 = -94 °C
P1
V1
(34,470 Pa) (473.18 mL)
P2
P2
V2
(13.13 mL)
1,242,000 Pa
V1
V2
T1
T2
31.4 L
25.0 L
296.6 K
T2
236 K or
-37 oC
P1 = 12.0 atm
V1 = 23.0 L
T1 = 200. K
P2 = 14.0 atm
V2 = ? L
T2 = 300. K
P1 V 1
T1
=
P2 V 2
T2
P1 V1 T2 = P2 V2 T1
V2 = 12.0 atm x 23.0 L x 300 K
14.0 atm x 200 K
= 29.6 L
Pass the
Clicker!!!
1.
2.
3.
4.
5.
2.00 atm
0.500 atm
1.08 atm
0.923 atm
Not listed
1.
2.
3.
4.
5.
-124oC
149oC
119oC
-154oC
Not listed
1.
2.
3.
4.
5.
.00687 mL
44.4 mL
6.87 mL
5220 mL
Not listed
The End!!!