Lecture_8 - 1 Gases Todays Lecture 5.1 Early Experiments...

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Unformatted text preview: 1 Gases Todays Lecture 5.1 Early Experiments 5.2 The Gas Laws of Boyle, Charles and Avogadro 5.3 The Ideal Gas Law 5.4 Gas Stoichiometry 5.5 Daltons Law of Partial Pressures 1 Pressure a balloon expands when it is inflated with air, but what keeps it in its distended shape? its not easy to measure the total force exerted by a gas so instead we consider the gas pressure Pa m N area force Pressure 2 = = = Vacuum the unit of pressure in the SI system is N/m 2 called the pascal 2 h = 760mm Hg for standard atmosphere note that a pascal is a rather small pressure unit, so units like the standard atmosphere (atm), mm Hg (called torr) and the kilopascal (kPa) are more commonly used 1 atm = 760 mm Hg = 760 torr = 101.325 kPa 2 The Gas Laws in 1662, working with air, Robert Boyle discovered the first of the gas laws, now known as Boyles law using a J-shaped tube closed at one end, he studied the relationship between the pressure of the trapped air and its volume PV = k (this equation is called Boyles law), where P = pressure of the gas, V = volume of the gas and k = constant at a specific temperature for a given sample of air 3 rearranging Boyles law gives: y = mx + b (in this case, y = V, x = 1/P, m = k and b = 0) P k V = Boyles Law Therefore, a plot of V vs. 1/P should give a straight line of slope k and an intercept of zero (Figure 5.4(b)). Figure 5.4(a) shows a plot of P vs. V (again, note the inverse relationship between pressure and volume). in Hg) 50 100 20 40 slope = k (in 3 ) 4 P ( 20 40 60 50 P P 2 V 2 V 1/ P (in Hg) 0.01 0.02 0.03 V (b) (a) Fig. 5.4 3 Boyles Law (contd) note that Boyles law (PV = k) only approximately describes the relationship between pressure and volume for a gas (i.e....
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This note was uploaded on 06/27/2009 for the course CHEM CHEM 121 taught by Professor Peggy during the Spring '09 term at Simon Fraser.

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Lecture_8 - 1 Gases Todays Lecture 5.1 Early Experiments...

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