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Section 13.1
Section 13.1
Describing the Properties of Gases
Describing the Properties of Gases
Objectives
A. Pressure
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
• Barometer – device that
measures atmospheric
pressure
– Invented by Evangelista
Torricelli in 1643
Section 13.1
Section 13.1
Describing the Properties of Gases
Describing the Properties of Gases
A. Pressure
A. Pressure
To learn about atmospheric pressure and how barometers work
To learn the units of pressure
To understand how the pressure and volume of a gas are related
To do calculations involving Boyle’s Law
To learn about absolute zero
To understand how the volume and temperature of a gas are related
To do calculations involving Charles’s Law
To understand how the pressure and temperature of a gas relate
To do calculations involving The Law of Gay-Lussac
To understand how the volume and number of moles of a gas are
related
11. To do calculations involving Avogadro’s Law
12. To see how the Ideal Gas Law is one way to combine the Gas Laws
Measuring Pressure
Atmospheric Pressure
Atmospheric Pressure
– Changing weather conditions
– Changing altitude
Section 13.1
Section 13.1
Describing the Properties of Gases
Describing the Properties of Gases
A. Pressure
A. Pressure
Units of Pressure
1 standard atmosphere
= 1.000 atm
= 760.0 mm Hg
= 760.0 torr
= 101,325 Pa
= 14.69 psi
Units of Pressure
• A manometer
measures the
pressure of a gas
in a container.
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Section 13.1
Section 13.1
Describing the Properties of Gases
Describing the Properties of Gases
B. Pressure and Volume: Boyle’s Law
B. Pressure and Volume: Boyle’s Law
• Robert Boyle’s experiment
Section 13.1
Section 13.1
Describing the Properties of Gases
Describing the Properties of Gases
B. Pressure and Volume: Boyle’s Law
B. Pressure and Volume: Boyle’s Law
• Graphing Boyle’s results
• This graph has the shape of half of a hyperbola with an
equation
PV = k
• Volume and pressure are inversely proportional.
– If one increases the other decreases.
Section 13.1
Section 13.1
Describing the Properties of Gases
Describing the Properties of Gases
B. Pressure and Volume: Boyle’s Law
C. Volume and Temperature: Charles’s Law
Another way of stating Boyle’s Law is
P1V1 = P2V2
(constant temperature and amount of gas)
• Graphing data for several gases
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Section 13.1
Section 13.1
Describing the Properties of Gases
Describing the Properties of Gases
C. Volume and Temperature: Charles’s Law
C. Volume and Temperature: Charles’s Law
• It is easier to write an equation for the relationship if the
lines intersect the origin of the graph.
• These graphs are lines with an equation
V = bT (where T is in kelvins, b is a constant)
– Use absolute zero for the temperature
• Volume and temperature are directly proportional.
– If one increases the other increases.
• Another way of stating Charles’s Law is
V1 = V2
T1
T2
(constant pressure and amount of gas (n))
Section 13.1
Section 13.1
Describing the Properties of Gases
Describing the Properties of Gases
C. Pressure and Temperature: Law of Gay-Lussac
D. Volume and Moles: Avogadro’s Law
• These graphs are lines with an equation
P = bT (where T is in kelvins, b is a constant)
• Pressure and temperature are directly proportional.
– If one increases the other increases.
• Another way of stating The Law of Gay-Lussac is
P1 = P2
T1
T2
(constant volume and amount of gas (n))
Section 13.1
Section 13.1
Describing the Properties of Gases
Describing the Properties of Gases
D. Volume and Moles: Avogadro’s Law
A. The Ideal Gas Law
• Volume and # of moles are directly proportional.
• Boyle’s Law
– If one increases the other increases.
– V = an
– constant temperature and pressure, a = a constant
• Another way of stating Avogadro’s Law is
V1 = V2
n1
n2
(constant temperature and pressure)
• Charles’s Law
• Avogadro’s Law
V = k (at constant T and n)
P
V = bT (at constant P and n)
V = an (at constant T and P)
We can combine these equations to get
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Section 13.1
Section 13.1
Describing the Properties of Gases
Describing the Properties of Gases
A. The Ideal Gas Law
C. Pressure, Volume and Temperature: The Combined Gas Law
Rearranging the equation gives the ideal gas law
PV = nRT
R = 0.08206 L atm
mol K
P must be in atm, V must be in L, T must be in kelvins, n is
in moles
• A Combination Law can be derived from the Ideal Gas Law
– All the variables are interrelated.
• The Combined Gas Law is
P1V1 = P2V2
n1T1
n2T2
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