Ch. 12 - Gases
II. The Gas
Laws
BOYLES
CHARLES
GAYLUSSAC
A. Boyle’s Law
 The
pressure and volume
of a gas are inversely
related
• at constant mass & temp
P1V1=P2V2
P
V
A. Boyle’s Law
B. Charles’ Law
 The
volume and absolute
temperature (K) of a gas
are directly related
• at constant mass &
pressure
V
V1 =V2
T 1 = T2
T
B. Charles’ Law
C. Gay-Lussac’s Law
 The
pressure and absolute
temperature (K) of a gas
are directly related
• at constant mass &
volume
P1 = P2
T1 T2
P
T
D. Combined Gas Law
P 1V 1
T1
=
P 2V 2
T2
P 1 V 1T 2 = P 2V 2 T 1
E. Gas Law Problems
A
gas occupies 100. mL at 150.
kPa. Find its volume at 200. kPa.
BOYLE’S LAW
GIVEN: P V
V1 = 100. mL
P1 = 150. kPa
V2 = ?
P2 = 200. kPa
WORK:
P1V1T2 = P2V2T1
(150.kPa)(100.mL)=(200.kPa)V2
V2 = 75.0 mL
E. Gas Law Problems
gas occupies 473 cm3 at 36°C.
Find its volume at 94°C.
A
CHARLES’ LAW
GIVEN: T V
V1 = 473 cm3
T1 = 36°C = 309K
V2 = ?
T2 = 94°C = 367K
WORK:
P1V1T2 = P2V2T1
(473 cm3)(367 K)=V2(309 K)
V2 = 562 cm3
E. Gas Law Problems
A
gas’ pressure is 765 torr at 23°C.
At what temperature will the
pressure be 560. torr?
GAY-LUSSAC’S LAW
GIVEN: P T WORK:
P1 = 765 torr
P1V1T2 = P2V2T1
T1 = 23°C = 296K (765 torr)T2 = (560. torr)(309K)
P2 = 560. torr
T2 = 226 K = -47°C
T2 = ?
F. STP
STP
Standard Temperature & Pressure
0°C
273 K
-OR-
1 atm
101.325 kPa
E. Gas Law Problems
gas occupies 7.84 cm3 at 71.8 kPa &
25°C. Find its volume at STP.
A
COMBINED GAS LAW
GIVEN: P T V WORK:
V1 = 7.84 cm3
P1V1T2 = P2V2T1
P1 = 71.8 kPa
(71.8 kPa)(7.84 cm3)(273 K)
T1 = 25°C = 298 K
=(101.325 kPa) V2 (298 K)
V2 = ?
P2 = 101.325 kPa V2 = 5.09 cm3
T2 = 273 K
Solve
 Divers
get “the bends” if they come up
too fast because gas in their blood
expands, forming bubbles in their blood.
If a diver has 0.05 L of gas in his blood
under a pressure of 250 atm, then rises
instantaneously to a depth where his
blood has a pressure of 50.0 atm, what
will the volume of gas in his blood be?
Do you think this will harm the diver?
Solve
 On
hot days, you may have noticed
that potato chip bags seem to
“inflate”, even though they have not
been opened. If I have a 250 mL
bag at a temperature of 19 0C, and
I leave it in my car which has a
temperature of 600 C, what will the
new volume of the bag be?
Solve
A
gas is heated from 263.0 K to
298.0 K and the volume is
increased from 24.0 liters to 35.0
liters by moving a large piston
within a cylinder. If the original
pressure was 1.00 atm, what would
the final pressure be?
Solve
A
gas with a volume of 4.0L at a
pressure of 205kPa is allowed to
expand to a volume of 12.0L. What
is the pressure in the container if
the temperature remains constant?
Solve
A
gas has a pressure of 699.0 mm
Hg at 40.0 °C. What is the
temperature at standard pressure?
Solve
I
have added 15 L of air to a
balloon at sea level (1.0 atm). If I
take the balloon with me to Denver,
where the air pressure is 0.85 atm,
what will the new volume of the
balloon be?