Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 A Gas 4 Uniformly fills any container. 4 Mixes completely with any other gas 4 Exerts

Copyright©2000 by Houghton Mifflin Company. All rights reserved.

1

A Gas

Uniformly fills any container.

Mixes completely with any other gas

Exerts pressure on its surroundings.


2

Pressure

is equal to force/unit area

SI units = Newton/meter2 = 1 Pascal (Pa)

1 standard atmosphere = 101,325 Pa

1 standard atmosphere = 1 atm =

760 mm Hg = 760 torr


3

Figure 5.2A Torricellian Barometer


4

Figure 5.3A Simple Manometer


5

Boyle’s Law*

Pressure Volume = Constant (T = constant)

P1V1 = P2V2 (T = constant)

V 1/P (T = constant)

(*Holds precisely only at very low pressures.)


6

Figure 5.4A J-Tube Similar to the One Used by Boyle


7

Figure 5.5Plotting Boyle’s Data from Table 5.1


8

Figure 5.6 A Plot of PV versus P for Several Gases at Pressures Below 1 ATM


9

A gas that strictly obeys Boyle’s Law is called an ideal gas.


10

Figure 5.7 A Plot of PV Versus P for 1 mol of Ammonia


11

Charles’s Law

The volume of a gas is directly proportional to temperature, and extrapolates to zero at zero Kelvin.

V = bT (P = constant)

b = a proportionality constant


12

Figure 5.8 Plots of V Versus T (ºC) for Several Gases


13

Figure 5.9 Plots of V Versus T


14

Charles’s Law

VT

VT

P1

1

2

2 ( constant)


15

Avogadro’s Law

For a gas at constant temperature and pressure, the volume is directly proportional to the number of moles of gas (at low pressures).

V = an

a = proportionality constant

V = volume of the gas

n = number of moles of gas


16

Figure 5.10: Balloons Holding 1.0 L of Gas at 25º C and 1 atm


17

Ideal Gas Law

An equation of state for a gas. “state” is the condition of the gas at a given

time.

PV = nRT


18

Ideal Gas Law

PV = nRT R = proportionality constant

= 0.08206 L atm mol

P = pressure in atm

V = volume in liters

n = moles

T = temperature in Kelvins

Holds closely at P < 1 atm


19

S/E 5.6 – 5.14

• Get thee to the Journal Notes.1


20

Standard Temperature and Pressure

“STP”P = 1 atmosphere

T = CThe molar volume of an ideal gas is 22.42 liters at STP


21

Figure 5.11A Mole of Any Gas Occupies a

Volume of Approximately 22.4 L at STP


22

Gas Stoichiometry (+ Gas Density)

• S/E 5.11 – 5.14: See Journal Notes.2


23

Dalton’s Law of Partial Pressures

For a mixture of gases in a container,

PTotal = P1 + P2 + P3 + . . .


24

Figure 5.12 Partial Pressure of Each Gas in a Mixture


25

Dalton’s Law of Partial Pressures (& the Mole Fraction concept)

• See the Journal Notes.3 and S/E 5.15 – 5.17

• Get thee there.


26

Kinetic Molecular Theory

1. Volume of individual particles is zero.

2. Collisions of particles with container walls cause pressure exerted by gas.

3. Particles exert no forces on each other.

4. Average kinetic energy Kelvin temperature of a gas.


27

The Meaning of Temperature

Kelvin temperature is an index of the random motions of gas particles (higher T means greater motion.)

(KE)32avg RT


28

Heat and Temperature

• TEMPERATURE is a measure of the AVERAGE K.E. of all the particles present.

• HEAT is the SUM of all the K.E. of all the particles present.


29

Root Mean Square Velocity

• (KE)avg = 3/2 RT (this shows the relation between temperature and average K.E.)

• See Journal Note 10/3/a3 /RT M


30

Effusion: describes the passage of gas into an evacuated chamber.

Diffusion: describes the mixing of gases. The rate of diffusion is the rate of gas mixing.


31

Rate of effusion for gas 1Rate of effusion for gas 2

2

1

MM

Distance traveled by gas 1Distance traveled by gas 2

2

1

MM

Effusion:Effusion:

Diffusion:Diffusion:


32

Real Gases

Must correct ideal gas behavior when at high pressure (smaller volume) and low temperature (attractive forces become important).


33

Real Gases

[ ]P a V nb nRTobs2( / ) n V

corrected pressurecorrected pressure corrected volumecorrected volume

PPidealideal VVidealideal


34

Chemistry in the Atmosphere

• See Journal Notes 10/3/b

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Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 A Gas 4 Uniformly fills any container. 4 Mixes completely with any other gas 4 Exerts