The Kinetic-Molecular Theory of Matter

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The Kinetic-Molecular Theory of Matter

• Objective 2.05

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Ideal Gases

• An imaginary gas that perfectly fits all the
  assumptions about kinetic molecular theory
• Kinetic Molecular Theory of Gases (KMT)
• explains the properties of gases

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Kinetic-Molecular Theory of Gases

• Assumptions about Ideal Gases
• particles are spread far apart
• mostly empty space
• Collisions are elastic collisions
• Particles are in continuous, random motion
• no forces of attraction or repulsion
• average kinetic-energy temperature

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However.

• Real Gases
• Do not follow KMT completely
• But we can use the KMT to describe them
• How they differ
• Occupy space
• Particles ARE attracted to each other (to some
  degree)
• Nonpolar gases deviate less than polar gases

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Nature of gases explained by KMT

• Expansion
• Fluidity
• Low Density
• Compressibility
• Diffusion

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Units of pressure

• Mm of Hg
• Torr
• Atmospheres (atm)
• Kilopascals (kPa)
• Pressure Unit Conversions
• 1 atm 760 mmHg 760 torr 101.3 kPa

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Units of Temperature

• Celsius (C)
• Kelvin (K)
• K C 273

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Standard temperature and pressure(STP)

• 1 atmOR
• 760 mm Hg
• 760 torr
• 101.3 kPa
• 273 K (0 C)

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The Gas Laws

• Combined Gas Law
• P1V1 P2V2
• T1 T2
• Used to determine pressure, temperature or volume
  of a gas

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Examples of Gas Problems using Combined Gas Law

• Pg. 315 Sample Problem 10-2
• Pg. 318 Sample Problem 10-3
• Pg. 320 Sample Problem 10-4
• Pg. 321 Sample Problem 10-5
• Remember T must be in Kelvin!
• Remember P units must be all the same!
• Whichever unit is constant cancels out!!!

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The Gas Laws

• Boyles Law
• Charles Law
• Gay Lussacs Law

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Ideal Gas Law

• Mathematical relationship among pressure, volume,
  temperature, and the number of moles of a gas
• PVnRT (given on Reference Guide)
• Pressure (P)
• Volume (V)
• Number of moles (n)
• Ideal gas constant (get from table on sheets)
• Temperature (T)

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Examples of Ideal Gas Problems

• Pg. 342 Sample Problem 11-3
• Pg. 343 Sample Problem 11-4
• Pg. 344 Sample Problems 11-5

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Daltons Law of Partial Pressures

• The total pressure of a mixture of gases is equal
  to the sum of the partial pressures of the
  component gases
• PTP1P2P3 (given on reference guide)
• Alsofor gas collected over water
• PT Pgas PH2O

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Example of Partial Pressures Problem

• Pg. 324 Sample Problem 10-6
• To get water pressure use
• Water Vapor Pressure Table Appendix A pg 899

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Avogadros Law for Gases

• Gases of the same volume, at the same temp and
  pressure, have the same number of molecules!
• n/V n/V
• A mole ratio in an equation can become a VOLUME
  ratio when all compounds are gases

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Example of Avogadros Law

• H2 (g) Cl2 (g) ? 2HCl (g)
• Mole Ratio 1 mol1mol2mol
• Volume Ratio 1L 1L 2L

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Molar Volume of A Gas

• At STP
• 1 mole of any gas 22.4 L
• New Branch on Mole Map