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CHEM 120: Introduction to Inorganic Chemistry

CHEM 120: Introduction to Inorganic Chemistry. Instructor: Upali Siriwardane (Ph.D., Ohio State University) CTH 311, Tele: 257-4941, e-mail: upali@chem.latech.edu Office hours: 10:00 to 12:00 Tu & Th ; 8:00-9:00 and 11:00-12:00 M,W,& F. Chapters Covered and Test dates.

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CHEM 120: Introduction to Inorganic Chemistry

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  1. CHEM 120: Introduction to Inorganic Chemistry Instructor: Upali Siriwardane (Ph.D., Ohio State University) CTH 311, Tele: 257-4941, e-mail: upali@chem.latech.edu Office hours: 10:00 to 12:00 Tu & Th ; 8:00-9:00 and 11:00-12:00 M,W,& F

  2. Chapters Covered and Test dates • Tests will be given in regular class periods  from  9:30-10:45 a.m. on the following days: September 22,     2004 (Test 1): Chapters 1 & 2 • October 8,         2004(Test 2):  Chapters  3, & 4 • October 20,         2004 (Test 3): Chapter  5 & 6 • November 3,        2004 (Test 4): Chapter  7 & 8 • November 15,      2004 (Test 5): Chapter  9 & 10 • November 17,      2004 MAKE-UP: Comprehensive test (Covers all chapters • Grading: • [( Test 1 + Test 2 + Test3 + Test4 + Test5)] x.70 + [ Homework + quiz average] x 0.30 = Final Average •                               5

  3. Chapter 6. States of Matter: Gases, Liquids, and Solids • Describe the behavior of gases : Boyle's law, Charles's law, combined gas law, Avogadro's law, the ideal gas law, and Dalton's law. 2. Use gas law equations to calculate conditions and changes in conditions of gases. 3. Describe the major points of the kinetic molecular theory of gases. 4. Explain the relationship between the kinetic molecular theory and the physical properties of macroscopic quantities of gases. 5. Describe properties of the liquid state. 6. Describe the processes of melting, boiling, evaporation, and condensation. 7. Describe the dipolar attractions known collectively as London dispersion (van der Waals) forces. 8. Describe hydrogen bonding and its relationship to boiling and melting temperatures. 9. Relate the properties of the various classes of solids (ionic, covalent, molecular, and metallic) to the structure of these solids.

  4. States of matter • By changing the temperature (and pressure) all matter can exist as a solid, as a liquid and as a gas. • There are forces of attraction (which we learn about later) btn cmpds that determine what physical state (gas, liquid, solid) we find the cmpd in at a given temperature.

  5. Temperature gives molecules kinetic energy. ______ the temp the ________ the kinetic energy. • If the strength of attractive forces btn molecules is much larger than the kinetic energy due to temp the cmpd will be a ________ • If the molecules’ kinetic energy due to temp is much greater than the attractive forces btn molecules the cmpd will be a _______ • If the attractive forces and the energy due to temp are similar the cmpd will be a _______

  6. Elements That Exist as Gases at 25°C, 1 atm YOU READ AND BE RESPONSIBLE FOR THIS SECTION!

  7. Gas properties:

  8. Liquid properties:

  9. Solid properties: .

  10. 4. In general for the same substance density of a solid > density of a liquid > density of a gas • For water densityliquid > densitysolid (ice floats) • See table 6.1

  11. The gaseous state • We are going to describe a gas in terms of the pressure (P) it exerts, the volume (V) it occupies and its temperature (T). • Pressure is a • We live at the bottom of a sea of gas molecules which are constantly hitting us and exerting pressure on us.

  12. Lower Atmosphere a) Troposphere (bottom): close to earth. b) Stratosphere: most atmospheric ozone is concentrated in a layer in the stratosphere. Upper Atmosphere c) Mesosphere d) Thermosphere (top)

  13. The downward force on any surface area (say 1 in2)due to “air” is equal to the mass of the column of air above the area and is 14.7psi (lb/in2). • We measure the pressure of the atmosphere with a

  14. Pair = PHg in the barometer tube. The downward pressure of the mercury in the column is balanced by the outside atmospheric pressure pressing down on the mercury in the dish. • We define one atmosphere as the atmospheric pressure which

  15. 1 atm = • (1 torr = 1 mm Hg) • Express 528 mm Hg in atm • Express 2.86 atm in mm Hg and torr.

  16. Objectives • 4 easily measured macroscopic properties: V, T, P, n (# moles) • Now we want to develop a mathematical relationship btn P,V,T and the no. of moles (n) of a gas.

  17. Boyle’s law • Boyle (1660) did some experiments that showed as the pressure applied to a gas increases, the volume occupied by the gas decreases as long as the temperature and amt of gas is held constant.

  18. Plot for an inverse relationship

  19. or P 1/V and V 1/P • PV = k1 where k1 is a proportionality constant that is • PiVi = k1 and PfVf =k1 so • PiVi = PfVf at the same temp and no.moles of gas

  20. Gases follow Boyle’s law best (PV=k) at • . • complete Pi(atm) Pf(atm) Vi(L) Vf(L) • 1.0 0.50 ? 0.30 • 1.0 2.0 0.75 ? • What happens to the volume if you triple the pressure at constant temp and no. moles?

  21. Charles’ Law, T and V • Charles, a hot air balloonist, (1800’s) investigated how V and T (temperature in K) were related. • He found that as the temperature of the gas increased, the volume occupied by the gas also increased as long as the pressure and amt of the gas were held constant.

  22. plot for direct relationship

  23. or V T and V = k2T where k2 is a proportionality constant that depends on the • Remember to convert from oC to K

  24. Charles’ Law • V = k2T • V/T = k2 • k2 = proportionality constant • independent of identity of gas • requires constant P and n • Vi/Ti = k2 and Vf/Tf = k2 so • Vi/Ti = Vf/Tf • excellent approximation at

  25. What happens to the volume when the temp in Kelvin is tripled at constant P and n?

  26. Avogadro’s Law, V and n • Avogadro found that the volume of a gas increased as the amt of the gas increased when the pressure and temp were held constant. (balloon) • V n or V = k3n direct relationship

  27. V  n • V = k3n • V/n = k3 • Vi/ni = Vf/nf • holds best at

  28. Upshot of Avogadro’s Law • Equal volumes of gases under the same conditions of temp and pressure contain equal nos. of particles. • Equal moles of all gases under the same conditions of temp and pressure have the same volume.

  29. The Ideal Gas Law • Boyle: V 1/P • Charles: V  T • Avogadro: V n

  30. An ideal gas obeys the gas laws we have developed. A real gas may deviate somewhat from these laws. But under conditions of _____________________, these laws are obeyed. The reason for this will be discussed later.

  31. STP (standard temp and pressure) • It is found that 1 mol of a gas occupies a volume of • Substituting the molar volume at STP in PV=nRT

  32. we get

  33. Molar volume • V of one mole of gas at STP = 22.4 L • Same V regardless of identity of gas! • but • 22.4 L of N2 • 22.4 L of CH4(g)

  34. Gas densities • d = • At STP • 1 mol of H2 has a mass of 2.0 g so dH2 = • 1 mol of O2 has a mass of 32.0 g so dO2 = • 1 mol of CO has a mass of 28.0 g so dCO =

  35. The ideal gas law contains all the other laws.

  36. The temp has to be in • In the comparative laws (Boyle’s, Charles’, etc) pressure and volume just have to be in the same units. n has to be in moles • In the ideal gas law the units are as specified before.

  37. Problems • A sample of nitrogen gas kept in a container of volume 2.3L and at a temp of 32oC exerts a pressure of 4.7 atm. Calc the no. of moles and the mass of gas present.

  38. A balloon has a volume of 43.0L at 20oC. What is its volume at -5oC? • A syringe has a volume of 10.0mL at 14.7psi. If the tip is blocked so that air can’t escape, what pressure is required to decrease the volume to 2.00mL? • If 20.0g of N2 gas has a volume of 4.00L and a pressure of 6.00atm, what is its temp?

  39. Which sample contains more molecules: 2.0L of CO2 at 300K and 500 mm Hg or 1.5L of N2 at 57oC and 760 mm Hg? Which sample weighs more? • An aerosol can has an internal pressure of 3.75atm at 25oC. What temp is required to raise the pressure to 16.6atm?

  40. A compressed-air tank carried by scuba divers has a volume of 8.0L and a pressure of 140 atm at 20oC. What is the volume of air in the tank at 0oC and 1.00atm pressure (STP)? • Cyclopropane. C3H6, is used as a general anesthetic. If a sample of cyclopropane is stored in a 2.00 L container at 10.0 atm and 25.0oC is transferred to a 5.00 L container at 5.00 atm, what is its resulting temp?

  41. What is the effect on a gas if you simultaneously: • a) halve its pressure and double its Kelvin temp • b) double its pressure and double its Kelvin tempereature.

  42. What volume will 818 g of sulfur hexafluoride gas occupy if the temperature and pressure of the gas are 128oC and 9.4 atm? • At what temp will 2.00 mol He fill a 2.00 L container at STP?

  43. 6.34: How many grams of helium must be added to a balloon containing 8.00 g of helium gas to double its volume. Assume no temp or pressure change.

  44. Dalton’s Law of Partial Pressures • Dalton (1803) said in a mixture of gases, each gas exerts a pressure as if it were present alone in the container. The pressure each gas exerts is called

  45. Dalton’s Law of Partial Pressures • For gas mixtures • Partial Pressure –pressure of an individual gas component in a mixture • Dalton’s Law of Partial Pressure – total pressure of a mixture of gases is the sum of the pressures that each gas would exert if it were present alone

  46. The mixture of gases as well as each gas obeys the ideal gas law and all of the other laws.

  47. The partial pressure of CH4(g) is 0.225atm and C2H6(g) is 0.165 atm in a mixture of the two gases. What is the total pressure? • A gas mixture has three components, N2, O2 and He. If the total pressure of the mixture is 0.78 atm and the partial pressure of N2 and He are 0.40 atm and 0. 18 atm respectively, what is the partial pressure of the O2 in the mixture?

  48. Kinetic Molecular Theory of Gases • There are several basic hypotheses that are used to explain the behavior of gases. • 1.Volume occupied by gas molecules themselves is negligible compared to the total volume occupied by the gas itself. (Gas molecules are though of as point masses: have mass but occupy no volume.)

  49. 2.The molecules of a gas are in constant, rapid, random straight line motion (Brownian motion) with no attractive forces btn the the molecules. • 3.The collisions the molecules make with themselves and with the walls of the container are elastic collisions. In other words energy is transferred from one molecule to another in a collision but the total energy of the molecules stays the same.

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