Gases

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# Gases - PowerPoint PPT Presentation

Gases. http:// www.mhhe.com/physsci/chemistry/animations/chang_7e_esp/gam2s2_6.swf. Section 1 – The Gas Laws. 1. Use the kinetic-molecular theory to explain the behavior of gases. 2. State, apply, & calculate the 3 following gas laws:. a. Boyle’s Law. b. Charles’s Law.

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## Gases

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Gases

http://www.mhhe.com/physsci/chemistry/animations/chang_7e_esp/gam2s2_6.swf

Section 1 – The Gas Laws

1. Use the kinetic-molecular theory to explain the behavior of gases

2. State, apply, & calculate the 3 following gas laws:

a. Boyle’s Law

b. Charles’s Law

c. Gay-Lussac’s Law

A. The Kinetic-Molecular Theory

1. Gas particles do NOT attract or repel

2. Gas particles are small; virtually no volume

3. Gas particles are in constant, random motion

4. Kinetic energy is transferred during the elastic collisions

• All gases have same averagekinetic energy at given temp

B. The Nature of Gases

1. Actual gases do not always obey the kinetic-molecular theory

2. The KMT is based on 4 factors:

a. Temperature (measured in Kelvin) [oC + 273 = K]

b. Pressure (measured in atm, kPa, etc.) [1atm = 101.3kPa = 760 mmHg or torr]

c. Volume (measured in liters or mL)

d. Amount of Gas (measured in moles)

http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/gaslaw/boyles_law_graph.htmlhttp://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/gaslaw/boyles_law_graph.html

C. Boyle’s Law

1. Temperature held CONSTANT

2. Found inverse relationship between pressure & volume

3. P1 V1 = P2 V2

P1 V1 = P2 V2

Sample Problem 1:If the pressure of helium gas in a balloon has a volume of 4.0 L at 210 kPa, what will the pressure be at 2.5 L?

340 kPa

Complete Practice Problems: #1 - #5

http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/gaslaw/charles_law.htmlhttp://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/gaslaw/charles_law.html

http://www.marymount.k12.ny.us/marynet/06stwbwrk/06gas/2slyscharles/2slysflash.html

D. Charles’s Law

1. Pressure held CONSTANT

2. Found direct relationship between temperature & volume

3. V1 = V2

T1

T2

http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/gaslaw/charles_law.html

V1 = V2

T1

T2

Sample Problem 2:A gas sample at 40 oC occupies a volume of 2.32 L. If the temperature is increased to 75 oC, what will be the final volume?

2.58 L

Complete Practice Problems: #6 - #8

http://www.marymount.k12.ny.us/marynet/06stwbwrk/06gas/1amcslussac/amcsgaylussac.htmlhttp://www.marymount.k12.ny.us/marynet/06stwbwrk/06gas/1amcslussac/amcsgaylussac.html

E. Gay-Lussac’s Law

1. Volume held CONSTANT

2. Found direct relationship between temperature & pressure

3. P1 = P2

T1

T2

What would a graph look like for Gay-Lussac’s Law?

P1 = P2

T1

T2

Sample Problem 3:The pressure of a gas in a tank is 3.2 atm at 22 oC. If the temperature rises to 60oC, what will be the pressure in the tank?

3.6 atm

Complete Practice Problems: #9 - #11

Section 2 – The Combined Gas Law & Avogadro’s Principle

1. State, apply, & calculate the combined gas law

2. Relate number of particles and volumes using Avogadro’s Principle

A. The Combined Gas Law

1. Amount of Gas held CONSTANT

2. P1 V1 = P2 V2

T1

T2

3. This law combines which 3 laws?

http://kids.earth.nasa.gov/archive/air_pressure/balloon.html

Sample Problem 4:A gas at 110 kPa and 30 oC fills a container at 2.0 L. If the temperature rises to 80oC and the pressure increases to 440 kPa, what is the new volume?

0.58 L

Complete Practice Problems: #12 - #14

1. Equal volumes of gases at the same temperature and pressure contains equal number of particles

2. Molar volume = 22.4 L/mol at STP

3. STP (Standard Temp & Pressure)

Temperature = 0 oC or 273 K

Pressure = 1 atm

Sample Problem 5:Calculate the volume that 0.881 mol of a gas at STP will occupy.

19.7 L

Complete Practice Problems: #15 - #17

Section 3 – The Ideal Gas Law

1. State, apply, & calculate the ideal gas law

2. State, apply, & calculate Dalton’s Law of Partial Pressure

3. State, apply, & calculate Graham’s Law of Effusion

http://www.chemistry.ohio-state.edu/betha/nealGasLaw/fr2.1.html

A. The Ideal Gas Law

1. Contains ALL variables

2. P V = n R T

• WhereP = pressure (depends on R)

V = volume (liters)

n = amount of gas (moles)

R = ideal gas constant (depends on pressure)

T = temperature (Kelvin)

62.8 L

Sample Problem 7:Calculate the moles of a gas at STP with a volume of 238 L.

10.6 mol

Sample Problem 8:Calculate the number of moles of gas contained in a 3.0 L vessel at 27 oC with a pressure of 1.50 atm.

0.18 mol

Complete Practice Problems: #18 - #20

B. Dalton’s Law of Partial Pressure

1. Contains only pressure

2. Where pressure must be in the same units

3. Ptotal = P1 + P2 + P3 + . . .

4. Sample Problem 9:If the total pressure of a mixture of oxygen & nitrogen gases was 820 mmHg, how much pressure would nitrogen exert if oxygen had 580 mmHg?

240 mmHg

Complete Practice Problems: #21 - #22

C. Graham’s Law of Effusion

1. Contains rates & masses of gases

2. Rate A = Mass B

Rate B

Mass A

• WhereRate is measured in m/s Mass is measured in grams

Sample Problem 8:If neon travels at 400. m/s, estimate the average speed of butane (C4H10) at the same temperature.

235 m/s

Sample Problem 9:Chlorine has a velocity of 0.0380 m/s. What is the average velocity of sulfur dioxide under the same conditions?

0.0400 m/s