Combined Gas Law When the three different laws just discussed are analyzed, what would they be if they are all combined? PV = k1 V/T=k2 P/T = k3

Combined Gas Law PV/T = k4 If the number of moles remains constant, we can solve for any of the other variables P1V1/T1= P2V2/T2 Also used is Standard Temperature and Pressure (STP) Standard Temperature is 0oC Standard Pressure is 1.00atm

Combined Gas Law At a pressure of 780.0 torr and 24.2oC, Xenon has a volume of 0.350L. What will the volume be at STP? First change temperature to Kelvin 24.2oC + 273 = 297.2 K P1V1/T1= P2V2/T2 (780.0torr)(0.350 L)/(297.2K) = (760.0torr)V2/(273K) V2 = 0.330 L

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

Graham’s Law of Diffusion In Graham’s Law of Diffusion, we will analyze the kinetic energy of two different gases Kinetic energy formula is 1/2mv2 m is the mass (in this case molar mass) v is the velocity of the molecule Graham’s Law states that the kinetic energy of the first gas will equal the kinetic energy of the second gas m1v12= m2v22

Graham’s 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 32.00 g/mol (O2) Molar mass of SF6 is 146.07 g/mol m1v12= m2v22 (32.00 g/mol)(480 m/s)2= (146.07 g/mol) v2 v = 224 m/s

Dalton’s Law of Partial Pressures Dalton’s 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 PT = P1 + P2 + P3 + …… A 42.0 mL sample of hydrogen is collected over water at 30.0oC. What is the total pressure if the pressure of the dry gas 845.0 torr and the vapor pressure of water at 30.0oC is 18.6 torr? PT = 845.0 torr + 18.6 torr PT = 863.6 torr