Chapter 10.1 & 11
Kinetic-Molecular Theory
&
Gas Laws
Kinetic Molecular Theory of
Matter
• Particles of matter are always in motion’
• Explains the properties of solids, liquids &
gases
Kinetic-Molecular Theory of
Gases
1) Gases consist of large numbers of tiny
particles that are far apart relative to their
size
- most of the volume in a gas is empty
space
2) Elastic collisions occur between gas
particles when the particles collide
- no net loss of KE(kinetic energy) occurs
@ constant Temp.
Kinetic-Molecular Theory of
Gases
3) Gas particles are in constant, rapid,
random motion
4) There are no forces of attraction or
repulsion between gas particles
5) The average K.E. of a gas depends on
the temperature of the gas
Types of Gases
• Ideal Gas- an imaginary gas that perfectly
fits all 5 assumptions
• Real Gas- a gas that does not meet all 5
assumptions
* Nobel gases are the
most like ideal gases
Kinetic Energy(K.E.)
• Kinetic Energy- energy of motion
KE = ½
2
mv
Mass of gas
particle
Velocity(speed)
of gas particle
Nature & Properties of Gases
•
•
•
•
•
Expansion- expand to fill their container
Fluidity- gases can flow, they are fluids
Low Density- molecules are far apart
Compressibility- Pressure = Volume
Diffusion- spreading out of molecules in a
random fashion
• Effusion- gas particles under pressure
escape through a hole “leaking out”
Pressure
• Pressure(P): the force per unit area on a
surface
Ex: Pressure = Force / Area
Pressure vs. Area: Inverse Proportion
Pressure vs. Force: Direct Proportion
Measuring Pressure:
• Barometer- measures atmospheric
pressure
Units of Pressure
mmHg- millimeters mercury atm- atmospheres
Pa- pascals
kPa- kilopascals
torr- Torr
1.0 atm = 760 mmHg
1.0 atm = 101.325 kPa
1.0 torr = 1.0 mmHg
STP: Standard Temperature &
Pressure
• STP represents standardized conditions for
measuring and recording temp. & pressure
STP = 1.0 atm & zero(0) degrees Celsius
Ex: 0.830 atm = ____ mmHg
0.830 atm = ____ kPa
795 mmHg = ____ atm
103.1 kPa = ____ atm
Kelvin Temperature Scale
Kelvin(K) = 273
• Absolute Zero = 0 K or -273 *C
C
*
Gas Laws
• The gas laws are simple mathematical
relationships between volume, temp,
pressure, and moles of a gas.
***Combined Gas Law:
Combined Gas Law
Gas Law Problems
Ex:
50.0 L of gas @ 25.0*C and 1.08 atm
Find Volume(V2) @ 10*C and 0.855 atm
Dalton’s Law of Partial Pressures
• The pressure of each gas in a mixture is a
partial pressure
• The total pressure of a mixture of gases is
equal to the sum of the partial pressures
Equation:
PT = P1 + P2 + P3 …
Gas Collected by Water
Displacement
• Gases collected by water displacement
are not pure, they bare a mixture of gas
and water vapor
• Water vapor also exerts pressure within a
container
Law of Combining Volumes of
Gases
• At a constant temperature and pressure,
the volumes of reactants and products can
be expressed using small whole # ratios ; )
Ex:
H2 (g) + Cl2 (g)  2 HCl (g)
Avogadro’s Law
• Equal volumes of gases at the same
temperature and pressure contain equal
numbers of molecules!!!
Ex:
Molar Volume of Gases
• The volume occupied by one mole of any
gas at STP is the standard molar volume
Standard Molar Volume = 22.4 L/mol
***Final Component of the
Mole Road!!!
Moles
multiply by 22.4 L/mol
@ STP
divide by 22.4 L/mol
Volume
(L)
Sample Problems
Ex:
Given: 0.0680 mol of O2 (g)
Find: Volume in L @ STP
Ex:
Given: 98.0 mL of SO2 @ STP
Find: mass of SO2 in grams
Ideal Gas Law
- The “perv-nert” equation
PV = nRT
Ideal Gas Constant(R)
R = 0.0821 L*mol/atm*K
• Make sure units are L, mol, atm, & K
• Convert if necessary
Ex: 0.50 mol of N2(g) are contained in a 10.0 L
flask @ 298 K.
Find the Pressure(P) in atm
Density(D) & Molar Mass(M)
Density
Molar Mass
D = m/V
or
D = MP/RT
M = mRT/PV
Ex:
Stoichiometry of Gases
a) Volume Volume
- Must have a balanced equation
- Treat volume ratios like mole ratios
Ex: __C3H8 + __O2  __CO2 + __H2O
Stoichiometry of Gases
b) Volume  Moles  Mass or vice-versa
Ex:
__C4H10 + __O2  __CO2 + __H2O
Stoichiometry of Gases
Ex:
__CaCO3  __CaO + __CO2
End of Chapter 10/11 Notes!!!