1 / 44

Chapter 10

Chapter 10. The Gaseous State. Setting the Stage – The Atmosphere. The atmosphere protects the planet and provides chemicals necessary for life. Oxygen supports metabolism and provides energy to living things.

elizabeththomas
Download Presentation

Chapter 10

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 10 The Gaseous State

  2. Setting the Stage – The Atmosphere • The atmosphere protects the planet and provides chemicals necessary for life. • Oxygen supports metabolism and provides energy to living things. • Nitrogen is incorporated into living organisms as amino acids and proteins. It also dilutes the oxidative effect of oxygen. • Carbon dioxide and water vapor act as greenhouse gases. • Stratospheric ozone absorbs harmful ionizing radiation from the sun. Malone and Dolter - Basic Concepts of Chemistry 9e

  3. Setting a Goal – Part AThe Nature of the Gaseous State and the Effects of Conditions • You will learn how the molecular nature of gases leads to predictable behavior, known as gas laws. Malone and Dolter - Basic Concepts of Chemistry 9e

  4. Objective for Section 10-1 • List the general properties of gases based on the postulates of the kinetic molecular theory. Malone and Dolter - Basic Concepts of Chemistry 9e

  5. 10-1 The Nature of Gases and the Kinetic Molecular Theory • Gases are compressible. • Gases have low density. • Gases mix thoroughly. • A gas fills a container uniformly and completely. • A gas exerts pressure uniformly on all sides of a container. Properties of Gases Malone and Dolter - Basic Concepts of Chemistry 9e

  6. Kinetic Molecular Theory • A gas is composed of very small particles called molecules which are widely spaced and have negligible volume. • The molecules of a gas are in constant, rapid, random motion colliding with each other and the walls of the container (pressure results from these collisions). Malone and Dolter - Basic Concepts of Chemistry 9e

  7. Kinetic Molecular Theory • All collisions involving gas molecules are elastic. • Gas molecules have negligibleattractive or repulsive forces between them. • The temperature of a gas is related to the average kinetic energy of the gas molecules. Malone and Dolter - Basic Concepts of Chemistry 9e

  8. Kinetic Molecular Theory • At the same temperature, different gases have the same kinetic energy. Malone and Dolter - Basic Concepts of Chemistry 9e

  9. Kinetic Molecular Theory • Since gases are mostly empty space, they are easy to compress. • Rapid motion accounts for why they mix thoroughly and completely. • By contrast, in solids and liquids, there is very little empty space and compression is much more difficult. Malone and Dolter - Basic Concepts of Chemistry 9e

  10. Kinetic Molecular Theory • The gas molecules are not attracted to each other so they do not clump together and instead fill the container completely and uniformly. • Two other properties of gases: • Diffusion – mixing of molecules of gas • Effusion – movement of gases through an opening or hole. Malone and Dolter - Basic Concepts of Chemistry 9e

  11. Graham’s Law • Rates of effusion or diffusion of gases are inversely proportional to the square roots of their molar masses. Malone and Dolter - Basic Concepts of Chemistry 9e

  12. Objectives for Section 10-2 • Define pressure. • Convert between units of pressure, and calculate how pressure affects the volume of a gas (Boyle’s Law). Malone and Dolter - Basic Concepts of Chemistry 9e

  13. 10-2 The Pressure of a Gas • Pressure is the force per unit area. • Originally measured with a barometer. Malone and Dolter - Basic Concepts of Chemistry 9e

  14. Units for Pressure • Pressure is measured in a variety of units, since the SI unit is cumbersome. • One of the most common units is fractions of atmospheric pressure at sea level – the atmosphere (atm). • One standard atm is defined as the pressure that will support 760 mm of Hg (mmHg or torr). Malone and Dolter - Basic Concepts of Chemistry 9e

  15. Units of Pressure – One Atmosphere (1 atm) • 760 mm Hg or 760 torr (used universally) • 101.324 kPa (the metric or SI unit) • 1.013 bar (used by physicists, astronomers and meteorologists) • 14.7 lb/in2 (used by some U.S. scientists) • 29.9 in Hg (used by some U.S. meteorologists) Malone and Dolter - Basic Concepts of Chemistry 9e

  16. Boyle’s Law of Pressure and Volume • There is an inverse relationship between pressure and volume at constant temperature. • A plot of P vs. 1/V is linear Malone and Dolter - Basic Concepts of Chemistry 9e

  17. Boyle’s Law Contd. • At constant temperature and number of moles of gas, we can calculate the effect of changes in pressure or volume on a gas. Malone and Dolter - Basic Concepts of Chemistry 9e

  18. Objectives for Section 10-3 • Using the gas laws, perform calculations involving the relationships among volume, pressure, and temperature. • Define the conditions known as STP. Malone and Dolter - Basic Concepts of Chemistry 9e

  19. 10-3 Charles’, Gay-Lussac’s and Avogadro’s Law • Charles found that the volume of a gas at constant pressure was directly proportional to temperature. • A plot of V vs. T is linear. Malone and Dolter - Basic Concepts of Chemistry 9e

  20. Absolute Temperature • If Celsius degrees are used for temperature, extrapolating to zero volume yields a temperature of -273.15 C. Malone and Dolter - Basic Concepts of Chemistry 9e

  21. Absolute Temperature • A real gas cannot be cooled infinitely (it condenses to a liquid or a solid). • However, the zero volume temperature does have significance, since it is theoretically the lowest possible temperature. • At this temperature, all translational motion (point to point motion) ceases. Malone and Dolter - Basic Concepts of Chemistry 9e

  22. The Kelvin Scale • Begins at 0 K (-273.15 C), known as absolute zero. • Kelvin scale has no negative values. • Magnitude of the Kelvin and Celsius degrees are the same, hence the conversion between the two is simple. (K = C + 273.15) Malone and Dolter - Basic Concepts of Chemistry 9e

  23. Charles’ Law for V and T Malone and Dolter - Basic Concepts of Chemistry 9e

  24. Gay-Lussac’s Law • Pressure is directly proportional to the Kelvin temperature at constant volume. Malone and Dolter - Basic Concepts of Chemistry 9e

  25. Charles’ and Gay-Lussac’s Laws • Both laws follow from the kinetic molecular theory of gases. • If T is increased, the speed of the gas molecule increases. • The gas molecule travels farther in a given time and strikes other objects with more force. • Hence either V or P must increase. Malone and Dolter - Basic Concepts of Chemistry 9e

  26. Combined Gas Law • Taking Boyle’s, Charles’ and Gay-Lussac’s Laws and combining them yields the combined gas law. • Note that T must be in K, and P1, P2 and V1, V2 must be in the same units. Malone and Dolter - Basic Concepts of Chemistry 9e

  27. Standard Temperature and Pressure • It is convenient for comparing gas properties to have a set of standard conditions. • Standard conditions show up in many areas of chemistry. • For gases • Standard temperature is 273 K or 0 C • Standard pressure is 760 torr or 1 atm Malone and Dolter - Basic Concepts of Chemistry 9e

  28. Avogadro’s Law • Equal volumes of gases at the same pressure and temperature contain equal numbers of molecules.or • The volume of a gas is proportional to the number of molecules (moles) of gas present at constant pressure and temperature. • V  n or V = constant × n Malone and Dolter - Basic Concepts of Chemistry 9e

  29. Summary Chart Malone and Dolter - Basic Concepts of Chemistry 9e

  30. Pioneers of the Gas Laws Lavoisier Priestley Gay-Lussac Avogadro Boyle Malone and Dolter - Basic Concepts of Chemistry 9e

  31. Setting a Goal - Part B Relationships Among Quantities of Gases, Conditions, and Chemical Reactions • You will learn to apply a generalized gas law to a variety of quantitative gas problems. Malone and Dolter - Basic Concepts of Chemistry 9e

  32. Objective for Section 10-4 • Using the ideal gas law, calculate one condition of the gas given the other stated conditions. Malone and Dolter - Basic Concepts of Chemistry 9e

  33. 10-4 The Ideal Gas Law • We can combine the three lawsV  1/P; V  T; V  n to yieldV  nT/P • If we introduce a constant R and rearrange, we get the ideal gas law (ideal in that it assumes the kinetic molecular theory)PV = nRTwhere R = 0.082057 L atm/K mol Malone and Dolter - Basic Concepts of Chemistry 9e

  34. Calculation of Volume Using the Ideal Gas Law • What is the volume of 1.00 mol of gas at STP? This is known as the molar volume Malone and Dolter - Basic Concepts of Chemistry 9e

  35. Objective for Section 10-5 • Using Dalton’s law, calculate the partial pressure of a gas. Malone and Dolter - Basic Concepts of Chemistry 9e

  36. 10-5 Dalton’s Law of Partial Pressures • The total pressure of a gas in a system is the sum of the partial pressure of each component gasPtotal = P1 + P2 + P3 + …where P1 is the pressure due to gas 1, etc. • For example, 21 % of the molecules in the atmosphere are oxygen molecules, therefore 21 % of the volume and the pressure of the atmosphere, is due to oxygene. g. P(O2) = 0.21 × 760 torr = 160 torr Malone and Dolter - Basic Concepts of Chemistry 9e

  37. Calculation of Total Pressure of a Mixture of Gases • What is the pressure (in atm) exerted by 12.0 g of N2, and 12.0 g of O2 in a 2.50 L flask at 25 oC? Malone and Dolter - Basic Concepts of Chemistry 9e

  38. Objectives for Section 10-6 • Using the molar volume, convert volume to moles and mass. • Calculate the density of a gas at STP. Malone and Dolter - Basic Concepts of Chemistry 9e

  39. 10-6 The Molar Volume and Density of a Gas • Molar volume of a gas (a property that is independent of the identity of the gas) • is 22.4 L at STP (ca 6 gallons) • is the volume of one mole of gas • contains Avogadro’s number (6.022 × 1023 molecules) • The molar volume contains one molar mass of gas, which does depend on the gas identity • Gas densities are of the order of g/L. Malone and Dolter - Basic Concepts of Chemistry 9e

  40. Calculating Mass and Density from Volume at STP • What is the mass of 4.55 L of O2 measured at STP? Density of O2 is then, 6.50 g/4.55 L = 1.43 g/L at STP Malone and Dolter - Basic Concepts of Chemistry 9e

  41. Objective for Section 10-7 • Perform stoichiometric calculations involving gas volumes. Malone and Dolter - Basic Concepts of Chemistry 9e

  42. 10-7 Stoichiometry Involving Gases • The ideal gas law allows us to convert a given volume of gas at a specified temperature and pressure into moles of gas. • For example, what mass of NaBH4 is needed to produce 50.0 L of H2 at STP? Malone and Dolter - Basic Concepts of Chemistry 9e

  43. Stoichiometry Involving Gases…Cont’d Malone and Dolter - Basic Concepts of Chemistry 9e

  44. Stoichiometry Involving Gases Malone and Dolter - Basic Concepts of Chemistry 9e

More Related