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Published byAaron Kelly Modified over 2 years ago

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Combined Gas Law When the three different laws just discussed are analyzed, what would they be if they are all combined? PV = k 1 V/T=k 2 P/T = k 3

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Combined Gas Law PV/T = k 4 If the number of moles remains constant, we can solve for any of the other variables P 1 V 1 /T 1 = P 2 V 2 /T 2 Also used is Standard Temperature and Pressure (STP) Standard Temperature is 0 o C Standard Pressure is 1.00atm

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Combined Gas Law At a pressure of torr and 24.2 o C, Xenon has a volume of 0.350L. What will the volume be at STP? First change temperature to Kelvin – 24.2 o C = K – P 1 V 1 /T 1 = P 2 V 2 /T 2 – (780.0torr)(0.350 L)/(297.2K) = (760.0torr)V 2 /(273K) – V 2 = L

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Diffusion and Effusion Diffusion is the movement of particles from high density to low density – Popping a balloon Effusion is the passage of gas molecules under pressure through a tiny opening – Nail in a tire

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Grahams Law of Diffusion In Grahams Law of Diffusion, we will analyze the kinetic energy of two different gases – Kinetic energy formula is 1/2mv 2 m is the mass (in this case molar mass) v is the velocity of the molecule – Grahams Law states that the kinetic energy of the first gas will equal the kinetic energy of the second gas m 1 v 1 2 = m 2 v 2 2

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Grahams Law of Diffusion Oxygen molecules have an average speed of 480 m/s at room temperature. At the same temperature, what is the average speed of molecules of sulfur hexafluoride? – Molar mass of Oxygen is g/mol (O 2 ) – Molar mass of SF 6 is g/mol – m 1 v 1 2 = m 2 v 2 2 – (32.00 g/mol)(480 m/s) 2 = ( g/mol) v 2 – v = 224 m/s

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Daltons Law of Partial Pressures Daltons law of partial pressures states that the total pressure of a mixture of gases is equal to the sum of the partial pressures of each gas P T = P 1 + P 2 + P 3 + …… A 42.0 mL sample of hydrogen is collected over water at 30.0 o C. What is the total pressure if the pressure of the dry gas torr and the vapor pressure of water at 30.0 o C is 18.6 torr? P T = P 1 + P 2 + P 3 + …… P T = torr torr P T = torr

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