Chapter 11: The
Behavior of Gases
Section 2:
The Gas Laws
Robert Boyle- Boyle’s Law
Pressure and Volume
Boyle’s Law states that the pressure and
volume of a gas at constant temperature are
inversely proportional
P1V1 = P2V2

If
If
If
If

pressure of gas ↑ - volume
pressure of gas ↓ - volume
volume of gas ↑ - pressure
volume of gas ↓ - pressure
of
of
of
of
gas
gas
gas
gas
↓
↑
↓
↑
According to the kinetic theory, if the
temperature of a gas is constant and the gas
is compressed, its pressure must rise

http://educationportal.com/academy/lesson/boylescharles-gay-lussacs-laws-pressurevolume-and-temperaturerelationships.html#lesson
Inverse Proportion
Boyle’s Law Practice problems
1)
60.0 mL of methane gas at 700 mm Hg
? mL of methane gas at 760 mm Hg
Use P1V1 = P2V2
(700 mm Hg) 60 mL = (760 mm Hg) ? mL
? mL = 55.3 mL
Boyles Practice
2)
1000 L at 1.0 atm
? L at 5.0 atm
Use P1V1 = P2V2
1.0 atm (1000 L) = 5.0 atm (? L )
? L = 200 L
Jacques Charles -Charles’s Law:
Temperature and Volume

Charles’s Law states that at constant
pressure, the volume of a gas is directly
proportional to its Kelvin temperature
V1 = V2
T1
T2
If volume increase, temperature increases
(vice-versa)
If volume decreases, temperature decreases
(vice-versa)

http://educationportal.com/academy/lesson/charles-lawgas-pressure-and-temperaturerelationship.html#lesson
Charles Law direct proportion
Charles’s Law Practice Problems
1) 3.0 L of He at 310 K
? L of He at 340 K
use V1 = V2
T1
T2
3.0 L = ? L
310 K
340 K
? L = (340K) 3.0L = 3.29 L
310 K
Charles Law Problems Cont
2) 4.0 L of methane at 30.0°C
? L of methane at 0°C
First convert °C to K: (Tk = Tc + 273)
0°C = 273 K
30.0°C = 30 + 273 = 303K
use V1 = V2
T1
T2
4.0 L = ? L
303K
273 K
? L = (273 K) 4.0L =
303 K
3.6 L
COMBINED GAS LAW
Combination of Boyle’s Law and Charles’s Law
You can solve for one variable (P, V or T),
regardless of the order in which the other two
changed.
P1V1 = P2V2
T1
T2
The set conditions for the combined gas law
problems are 0.00 °C and 1 atm- called
STANDARD TEMPERATURE AND PRESSURE or
STP
1) 2.7 L N2 at 121 kPa and 288 K
? L N2 at 202 kPa and 303K
Use
P1V1 = P2V2
T1
T2
121 kPa (2.7 L)
288 K
326.7 L ·kPa
288 K
= 202kPa ( ? L )
303 K
=
202kPa ( ? L)
303 K
1.13 L ·kPa = 0.66 kPa (? L)
K
K
? L = 1.70 L
LAW OF COMBINING GAS
VOLUMES

The observation that at the same
temperature and pressure, volumes of gases
combine or decompose in ratios of small
whole numbers

Gas Reactions show that volumes of gases
always react in ratios of small whole numbers
http://educationportal.com/academy/lesson/daltons-law-ofpartial-pressures-calculating-partial-totalpressures.html#lesson

Amedeo Avogadro




First to interpret the law of combining
volumes in terms of interacting particles
The volume of a gas at a given temperature
and pressure depends on the number of gas
particles
AVOGRADO’S PRINCIPLE states that equal
volumes of gases at the same temperature
and pressure contain equal numbers of
particles
http://educationportal.com/academy/lesson/molar-volumeusing-avogadros-law-to-calculate-thequantity-or-volume-of-a-gas.html#lesson