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Chpt_05_LE_student - Gases Chapter 5 Some Substances Found...

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1 Gases Gases Chapter 5 Chapter 5 Some Substances Found as Gases at 1 Some Substances Found as Gases at 1 atm atm and 25 and 25 ° C All gases have the following physical characteristics: SO 2 , **H 2 S, **HCN He, Ne, Ar, Kr, Xe, Rn NH 3 , NO, NO 2 , N 2 O F 2 , Cl 2 CO, CO 2 *O 2 , O 3 HF, HCl, HBr, HI H 2 , N 2 Compounds Elements * essential for our survial ** deadly poisons LE_Chem102A_01_Fall 2008 (Chapter 5)
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2 The Pressure of A Gas The Pressure of A Gas ± Pressure: result of the constant movement of the gas molecules and their collisions with the surfaces around them. Pressure = force per unit area ± The pressure of a gas depends on several factors ± number of gas particles in a given volume ± volume of the container ± average speed of the gas particles ± Mercury barometer invented by Evangelista Torricelli in 17 th centry is a device for measuring atmospheric pressure ± column of mercury supported by air pressure ± force of the air on the surface of the mercury balanced by the pull of gravity on the column of mercury ± average atmospheric pressure at sea level can support a column of mercury 760 mm in height A barometer gravity The Pressure of A Gas The Pressure of A Gas 29.92 inHg inches of mercury (in Hg) 760 mmHg millimeters of mercury (mmHg) 14.7 psi pounds per square inch (psi, lbs./in 2 ) 760 torr Torr (torr) 101,325 Pa Pascal (Pa) Average Air Pressure at Sea Level (1 atm) Common Units of Pressure Standard atmospheric pressure (1atm) = the pressure exerted by Earth’s atmosphere LE_Chem102A_01_Fall 2008 (Chapter 5)
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3 Measuring Sample Gas Pressure Measuring Sample Gas Pressure A manometer (mm) levels Hg in difference (mmHg) Pressure (mmHg) Pressure Pressure Pressure Pressure atmosphere gas h atmosphere gas + = + = ± the pressure of a gas trapped in a container can be measured with an instrument called a manometer ± manometers are U-shaped tubes, partially filled with a liquid, connected to the gas sample on one side and open to the air on the other ± a competition is established between the pressure of the atmosphere and the gas ± the difference in the liquid levels is a measure of the difference in pressure between the gas and the atmosphere for this sample, the gas has a larger pressure than the atmosphere Boyle Boyle ’s Law: The Pressure s Law: The Pressure -Volume Relationship Volume Relationship ± Boyle’s Law: pressure of a gas is inversely proportional to its volume ± constant T and amount of gas ± graph P vs V is curve ± graph P vs 1/ V is straight line ± as P increases, V decreases by the same factor ± P x V = constant ± P 1 x V 1 = P 2 x V 2 When you double the pressure on a gas, the volume is cut in half (as long as the temperature and amount of gas do not change) LE_Chem102A_01_Fall 2008 (Chapter 5)
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4 Boyle Boyle ’s Law Calculation s Law Calculation Example 1: A balloon is put in a bell jar and the pressure is reduced from 782 torr to 0.500 atm. If the volume of the balloon is now 2780 mL, what was it originally? Boyle
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Chpt_05_LE_student - Gases Chapter 5 Some Substances Found...

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