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Chemistry, The Central Science , 10th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten. Chapter 10 Gases. John Bookstaver St. Charles Community College St. Peters, MO 2006, Prentice Hall, Inc. Bell work. Turn your chapter 10 outline into the tray .

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## Chapter 10 Gases

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**Chemistry, The Central Science, 10th edition**Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten Chapter 10Gases John Bookstaver St. Charles Community College St. Peters, MO 2006, Prentice Hall, Inc.**Bell work**• Turn your chapter 10 outline into the tray. • List the properties of gases. How do they differ from solids and liquids? • What are some of the main formulas in this chapter?**Agenda**• Bell work • Discuss review project • Overview of chapter 10 • 10.1-10.6 • HW: Continue reviewing for test! Chapters 6-9, 10?; Thursday, Dec 1**Review project**• I’m in the midst of creating a rubric/guideline for a project. It’ll be student-led review during review week. You’ll work with a partner to create an outline of your chapter, sample problems, and a presentation of the material. Tomorrow you’ll get a description, rubric, and have time in class to work on it.**Breakdown**• You will be responsible for one of the following topic groupings: • Chapters 1-3 • Chapter 4 • Chapter 5 • Chapters 6 & 7 • Chapter 8 & 9**Pressure and volume**• What is the relationship between pressure and volume? • Inversely proportional • Meaning? • When one goes up, the other goes down**Temperature and volume**• What is the relationship between temperature and volume? • Directly proportional • Meaning? • When one goes up, the other goes up**Quantity and volume**• What is the relationship between quantity and volume? • Directly proportional • Meaning? • When one goes up, the other goes up**Equations**• PV=nRT • P1 V1 = P2 V2 • P1 V1 / T1 = P2 V2 / T2 • Ptotal = Pgas 1 + Pgas 2 + Pgas 3 + …. • Need mole fraction moles of gas 1/total moles of gas • Remember that you can get mass from n (# of moles) and you can find density as well**Start with PV=nRT**We know that n= mass/Molar mass Density is mass/V That’s what we want on one side of the equation**Kinetic Molecular Theory**Describes ideal gases 5 postulates Molecules in continuous, random motion Negligible volume No attractive forces between molecules Collisions are elastic Average kinetic energy is proportional to absolute temperature**Do larger molecules move faster or more slowly than smaller**molecules? Larger move more slowly Affects effusion rate and root mean square (speed of molecule with average KE)**Under what conditions do gases tend to deviate from ideal**behavior the most? High pressure Low temperature In general, why do gases deviate from ideal behavior? Gas molecules have finite volumes and molecules are attracted to one another**Characteristics of Gases**• Unlike liquids and solids, they • Expand to fill their containers. • Are highly compressible. • Have extremely low densities.**Gases are generally of very low molecular mass.**• Gases have high kinetic energies. • In gases, the distance between molecules is relatively large. • In gases, the attractions between molecules are large.**Gases are generally of very low molecular mass.**• Gases have high kinetic energies. • In gases, the distance between molecules is relatively large. • In gases, the attractions between molecules are large.**F**A P = Pressure • Pressure is the amount of force applied to an area. • Atmospheric pressure is the weight of air per unit of area.**Units of Pressure**• You should know: 760 torr = 760 mmHg 1atm = 760 torr 760 torr = 101.325 kPa**Units of Pressure**• Pascals • 1 Pa = 1 N/m2 • Bar • 1 bar = 105 Pa = 100 kPa**Units of Pressure**• mm Hg or torr • These units are literally the difference in the heights measured in mm (h) of two connected columns of mercury. • Atmosphere • 1.00 atm = 760 torr**The height of the column increases because atmospheric**pressure decreases with increasing altitude. • The height of the column decreases because atmospheric pressure decreases with increasing altitude. • The height of the column decreases because atmospheric pressure increases with increasing altitude. • The height of the column increases because atmospheric pressure increases with increasing altitude.**The height of the column increases because atmospheric**pressure decreases with increasing altitude. • The height of the column decreases because atmospheric pressure decreases with increasing altitude. • The height of the column decreases because atmospheric pressure increases with increasing altitude. • The height of the column increases because atmospheric pressure increases with increasing altitude.**Manometer**Used to measure the difference in pressure between atmospheric pressure and that of a gas in a vessel.**Standard Pressure**• Normal atmospheric pressure at sea level. • It is equal to • 1.00 atm • 760 torr (760 mm Hg) • 101.325 kPa**Boyle’s Law**The volume of a fixed quantity of gas at constant temperature is inversely proportional to the pressure.**PV = k**• Since • V = k (1/P) • This means a plot of V versus 1/P will be a straight line. As P and V areinversely proportional A plot of V versus P results in a curve.**The volume change cannot be predicted without knowing the**type of gas. • The volume change cannot be predicted without knowing the amount of gas. • As you double the pressure, the volume decreases to half its original value. • As you double the pressure, the volume increases to twice its original value.**The volume change cannot be predicted without knowing the**type of gas. • The volume change cannot be predicted without knowing the amount of gas. • As you double the pressure, the volume decreases to half its original value. • As you double the pressure, the volume increases to twice its original value.**V**T = k • i.e., Charles’s Law • The volume of a fixed amount of gas at constant pressure is directly proportional to its absolute temperature. A plot of V versus T will be a straight line.**Yes, because volume is proportional to temperature.**• No. The volume decreases but it doesn’t decrease to half because the volume is proportional to temperature on the Kelvin scale (not the Celsius scale).**Yes, because volume is proportional to temperature.**• No. The volume decreases but it doesn’t decrease to half because the volume is proportional to temperature on the Kelvin scale (not the Celsius scale).**V = kn**• Mathematically, this means Avogadro’s Law • The volume of a gas at constant temperature and pressure is directly proportional to the number of moles of the gas.**Combining these, we get**nT P V Ideal-Gas Equation • So far we’ve seen that V 1/P (Boyle’s law) VT (Charles’s law) Vn (Avogadro’s law)**Ideal-Gas Equation**The constant of proportionality is known as R, the gas constant.**nT**P nT P V V= R Ideal-Gas Equation The relationship then becomes or PV = nRT**At STP there is one mole or 6.022 1023 molecules**(Avogadro’s number). • At STP there is 1 mol of molecules. • At STP there are 22.4 mol of molecules. • More information is needed, because the number of molecules depends on the type of gas.**At STP there is one mole or 6.022 1023 molecules**(Avogadro’s number). • At STP there is 1 mol of molecules. • At STP there are 22.4 mol of molecules. • More information is needed, because the number of molecules depends on the type of gas.**Bell work**• Aluminum reacts with iodine. I have 5 moles of aluminum. How much iodine do I need to react completely with the aluminum? How much product can I expect?**Agenda**• Bell work • Overview of project • Time to work on project • HW: Finish sample problems in chapter 10, continue studying for Thursday’s test (chapters 6-10) • If you want your overviews, come see me after school and I’ll give them to you**Bell work**• A large natural-gas storage tank is arranged so that the pressure is maintained at 2.20 atm. On a cold day in December when the temperature is -15⁰C (4⁰F), the volume of the gas is 28,500 ft3. What is the volume of the same quantity of gas on a warm July day when the temperature is 31⁰C (88 ⁰F)?**Agenda**• Bell work • Finish chapter 10 • Time to work on HW problems and sample exercises • HW: Test on Thursday! Covers chapters 6-10! Don’t forget about your review projects!**n**V P RT = Densities of Gases If we divide both sides of the ideal-gas equation by V and by RT, we get**m**V P RT = Densities of Gases • We know that • moles molecular mass = mass n = m • So multiplying both sides by the molecular mass ( ) gives

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