Three More Laws

A. Ideal Gas Law The 4 th variable that considers the amount of gas in the system is P 1 V 1 T 1 n = P 2 V 2 T 2 n Equal volumes of gases contain equal numbers of moles (varies directly w/V). Add moles to the combination gas law

A. Ideal Gas Law You don’t need to memorize this value! You can calculate the # of n of gas at standard values for P, V, and T PV Tn = R (1 atm)(22.4L) (273K)(1 mol) = R UNIVERSAL GAS CONSTANT R= atm∙L/mol∙K R=8.315 kPa  L/mol  K

A. Ideal Gas Law You don’t need to memorize these values! UNIVERSAL GAS CONSTANT R= atm∙L/mol∙K R=8.315 kPa  L/mol  K PV=nRT

A. Example Problems 1. At what temperature will 5.00g of Cl 2 exert a pressure of 900 mm Hg at a volume of 750 mL? 2. Find the number of grams of CO 2 that exert a pressure of 785 mm Hg at a volume of 32.5 L and a temperature of 32 degrees Celsius. 3. What volume will 454 g of H 2 occupy at 1.05 atm and 25°C.

B. Graham’s Law Diffusion Diffusion – The tendency of molecules to move toward areas of lower concentration. Ex: air leaving tire when valve is opened Effusion Effusion – Passing of gas molecules through a tiny opening in a container

B. Graham’s Law Which one is Diffusion and which one is Effusion? Diffusion Effusion Tiny opening

C. Dalton’s Partial Pressure Law The total pressure of a mixture of gases equals the sum of the partial pressures of the individual gases. P total = P 1 + P 2 + P

C. Dalton’s Law Exmple problem: 1. Air contains oxygen, nitrogen, carbon dioxide, and trace amounts of other gases. What is the partial pressure of oxygen (P O 2 ) at kPa of total pressure if the partial pressures of nitrogen, carbon dioxide, and other gases are kPa, kPa, and 0.94 kPa. P O 2 = P total – (P N 2 + P CO 2 + P others ) = kPa – (79.10 kPa kPa kPa) = kPa