Unit 2, chap 5 - Gases Chapter 5 Pressure All gases exert...

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Gases Chapter 5
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Pressure All gases exert pressure This is due to the collisions of gas molecules with the walls of the container they fill The nearly steady rate at which the molecules collide with the wall causes a steady force on the wall, called pressure
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Pressure Evangelista Torricelli proved that the air in the atmosphere exerts pressure by designing the first barometer A tube filled with mercury was inverted into a dish Hg flowed out of the tube until the pressure of the Hg remaining in the tube was equal to the atmospheric pressure exerted on the surface of Hg in the dish A column of Hg approximately 760 mm tall remained in the tube
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Pressure Pressure is force per unit area (P = F/A) Common units are lbs/in 2 , N/m 2 N/m 2 is the SI unit of force, called a pascal (Pa) Other units of pressure are standard atmosphere (atm), millimeters mercury (mm Hg), and torr (in honor of Torricelli) 1 atm = 760 mm Hg = 760 torr = 101325 Pa
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Boyle’s Law By using a J shaped tube closed at one end, Boyle studied the relationship between pressure and volume of a gas He found that the product of the pressure and volume of the trapped gas is constant This can be expressed mathematically as PV = k where k is a constant
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Boyle’s Law can be used to calculate the new volume of a gas when the pressure is changed P i V i = P f V f Example: A sample of He has a volume of 400 mL under a pressure of 760 torr. What volume would it occupy under a pressure of 1520 torr? P
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This note was uploaded on 07/25/2011 for the course CH 301 taught by Professor Fakhreddine/lyon during the Spring '07 term at University of Texas at Austin.

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Unit 2, chap 5 - Gases Chapter 5 Pressure All gases exert...

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