Gases
Lecture 5.1
Kinetic Molecular Theory
1) All particles are in constant random motion
2)
3) The volume of the particles in a gas is negligible
4)
This equation relates the kinetic energy of any particle to its mass and velocity
We will attempt to use KMT to help explain many of the gas laws
Properties
Variable
Units
1) Quantity
n
moles
2)
3) Volume
V
Liters, L
4)
- sometimes given in celsius!
+/- 273 … no negative K!!
Pressure Units: 760 mm Hg = 760 torr = 1 atm = 101.3 kPa
- lots of other units … conversion time!!
Standard Temperature & Pressure (STP)
Temperature = 0 ºC or 273 K
Pressure = 1 atm
Pressure Units: 760 mm Hg = 760 torr = 1 atm = 101.3 kPa
Gas Laws
Lots of dead guys and their formulas that help us understand and work with gases!!
1) Avogadro’s Law
2) Boyle’s Law
3) Charles’ Law
4) Gay-Lussac’s Law
5) Combined Gas Law
6) Ideal Gas Law
7) Gas Density
8) Dalton’s Law of Partial Pressures
9) Graham’s Law
What the heck Mr. N this isn’t a law??
True! … but we still need to work with it
You’ve seen most of these before!!
Avogadro’s Law = V and n
- The volume of a gas is
- P and T held constant
V ∝ n
V1
n1
V2
n2
=
Boyle’s Law = V and P
- The volume of a gas is
- T and n held constant
★ P1 * V1 = P2 * V2 ★
Ex: A 1.53 L sample of a sulfur dioxide gas is held at 5.6 x 103 Pa. If the pressure changes to 1.5 x 104 Pa at a constant temperature, what will the new volume of the gas be?
Charles’ Law = V and T
- The volume of a gas is
- P and n held constant
V1
T1
V2
T2
=
MUST be in K!!
Recall:
K = C + 273
C = K − 273
Ex: A sample of gas at 15 ºC and 1 atm has a volume of 2.58 L. What volume will this gas occupy at 38 ºC and 1 atm?
Gay-Lussac’s Law = P and T
- The pressure on a gas is
- V and n held constant
P1
T1
P2
T2
=
MUST be in K!!
Ex: A gas is held at a pressure of 835 torr when the temperature is 303 K. If the temperature is raised to 410 K, what will the pressure on the gas be (in atm)?
Combined Gas Law= P, V and T
- A combination of Boyle’s law, Charles’ law, and Gay-Lussac’s law
- n held constant
P1 * V1
T1
=
P2 * V2
T2
Boyle’s Law!
Charles’ Law!
Gay-Lussac’s Law!
Ex: A 4.1 L sample of a gas is held at a pressure of 3.6 atm when the temperature is 280 K. What is the pressure if the temperature is lowered to 212 K and the volume is measured to be 2.3 L?