This document summarizes key concepts about gases from a chemistry textbook. It discusses the properties of gases, gas pressure, gas laws including Boyle's law, Charles' law, Gay-Lussac's law, Avogadro's law, and the ideal gas law. It also covers gas behavior such as diffusion and effusion according to Graham's law, and mixtures of gases based on Dalton's law of partial pressures.

1. Chapter 2 Gases

2. 12.1 Characteristics of Gases Properties of Gases because gas particles are far apart, gases are fluids (they can flow) gases have low density gases are highly compressible gases completely fill a container

3. 12.1 Characteristics of Gases Gas Pressure Rene Descarte (1596-1650): rejected idea of void or vacuum Pierre Gassendi (1592-1655): revived atomism; promoted idea of atoms moving in a void Evangelista Torricelli (1608-1647): built a mercury barometer in 1643; created a vacuum

4. Mercury Barometer

5. 12.1 Characteristics of Gases Gas Pressure Blaise Pascal (1623-1662): tested atmospheric pressure at prompting of Descarte; found that pressure drops with altitude; believed in the vacuum

6. 12.1 Characteristics of Gases Gas Pressure pressure is force divided by area force: Newton (1 kg  m/s 2 = 1 N) area: meter squared (m 2 ) pressure: Pascal (1 Pa = 1 N/1 m 2 ) for comparisons, standard temperature and pressure (STP): 0  C and 1 atm

7. Pressure Units

8. 12.1 Characteristics of Gases Kinetic-Molecular Theory gas particles are in constant, rapid, random motion particles far apart relative to size pressure due to collisions of particles with the walls of their container

9. 12.1 Characteristics of Gases Kinetic-Molecular Theory gas temperature is proportional to average kinetic energy gas molecules have a range of speeds increasing temperature shifts the distribution

10. Gas Molecules Energy Distribution

11. 12.2 The Gas Laws Measurable Properties of Gases P = pressure exerted by gas V = total volume occupied by gas T = temperature in kelvins of gas n = number of moles of gas

12. 12.2 The Gas Laws Robert Boyle (1627-1691): published The Spring of Air in 1660, which explained his most famous experiment Boyle put mercury in a j-tube (manometer), and saw that when he doubled the pressure, the volume of air in short end halved

13. Boyle’s Experiment

14. Boyle’s Law

15. 12.2 The Gas Laws Robert Boyle Boyle’s law: PV = k P 1 V 1 = P 2 V 2

16. Boyle’s Law

17. 12.2 The Gas Laws Jacques Charles: discovered that a gas’s volume is proportional to temperature at constant pressure in 1787 Charles’s law: V / T = k V 1 / T 1 = V 2 / T 2

18. Charles’s Law

19. 12.2 The Gas Laws Joseph Gay-Lussac (1778-1850): discovered in 1802 that increasing temperature at constant volume resulted in a proportional increase in pressure Gay-Lussac’s law: P = kT P / T = k P 1 / T 1 = P 2 / T 2

20. Gay-Lussac’s Law

21. 12.2 The Gas Laws Gay-Lussac’s law of combining volumes (1809): gases combine in simple proportions by volume, and volume of products is related to volume of reactants example 1: 2 volumes of H 2 react with 1 volume of O 2 to make 2 volumes of water allowed Avogadro to deduce diatomic molecules (and more)

22. Combining Volumes

23. 12.2 The Gas Laws Amadeo Avogadro (1776-1856): proposed in 1811 that equal volumes of all gases contain equal numbers of particles Avogadro’s law: V = kn 1 mol of any gas at 0  C and 1 atm occupies 22.41 L

24. Avogadro’s Law

25. 12.2 The Gas Laws Stanislao Cannizzaro (1826-1910): ~1858, deduced that Gay-Lussac’s law of combining volumes and Avogadro’s law could be used to calculate atomic and molecular weights relative to hydrogen; drew distinction between atoms and molecules; made a table of atomic weights

26. Gas Laws Summary

27. 12.3 Molecular Comp. of Gases Ideal Gas Law no gas perfectly obeys Boyle’s law, Charles’s law, Gay-Lussac’s law, or Avogadro’s law although not perfect, these laws work well for most gases and most conditions ideal gas : model gas that perfectly obeys gas laws

28. Ideal Gases vs. Real Gases

29. 12.3 Molecular Comp. of Gases Ideal Gas Law ideal gases do not condense to liquids at low temperatures do not have particles attracted to or repulsed by each other have particles of no volume do not exist

30. 12.3 Molecular Comp. of Gases Ideal Gas Law : combines four variables, P , V , T , and n , into one equation PV = nRT R is a proportionality constant R = 8.314 L  kPa mol  K

31. 12.3 Molecular Comp. of Gases Gas Behavior and Chemical Formulas Diffusion : movement of particles from high concentration to low concentration particles of lower mass diffuse more quickly than particles of higher mass diffusion increases entropy

32. 12.3 Molecular Comp. of Gases Gas Behavior and Chemical Formulas Effusion : passage of gas particles through a small opening Graham’s law: rate of diffusion and effusion of a gas are inversely proportional to the square root of the gas’s density

33. 12.3 Molecular Comp. of Gases Gas Behavior and Chemical Formulas Graham’s law, cont. where v A and v B are molecular speeds of gases A and B and M A and M B are the molar masses of gases A and B

34. 12.3 Molecular Comp. of Gases Gas Behavior and Chemical Formulas Graham’s law, cont. Graham’s law is easy to derive: solve the equation for the ratio of speeds between v A and v B

35. 12.3 The Gas Laws John Dalton (1766-1844): discovered that each gas in a mixture produces its own pressure as if it was alone Dalton’s law of partial pressure: total pressure of a mixture of gases is equal to the sum of the partial pressures of the component gases P total = P A + P B + P C