Gas Laws Study GuideNotes: Properties of solids, liquids, & gases: Solids o Particles very close together o Highest density o Lowest kinetic energy o Least amount of motion o Definite shape & volume Phase Changes Solid liquid: melting Liquid solid: freezing Gases: There are three main characteristics of gases – all of which are a result of the kinetic molecular theory which says: 1. all particles of a gas are in constant motion 2. as a result of this motion, random collisions occur, but gases are not attracted or repelled from each other 3. gases are much smaller than the distance between them. The characteristics of gases are: 1. volume: the amount of space a gas occupies – usually measured in liters or mL 2. Pressure: forcer per unit area – comes from particles banging into the side of the container. Measured in kilopascals, atmospheres, or mm of mercury. 3. Temperature: average kinetic energy of the particles of gas – measured in degrees celcius or Kelvin. **ALWAYS HAS TO BE IN KELVIN FOR GAS LAW PROBLEMS** 4. STP: standard temperature & pressure Pressure: 1 atm = 101.3 kPa = 760 mmHg (given on reference table) Temperature: 0°C = 273 K K = °C + 273 (given on reference table) Volume: 1 mole = 22.4 L Scientific Laws & Discoveries: 1. Dalton said that the total pressure of a gas is equal to the sum of the pressures of each part of the gas mixture. Dalton’s Law of Partial Pressure: Ptotal = P1 + P2 + P3 +… Liquids o Particles loosely held together o Moderate density o Moderate kinetic energy o Some motion o Definite shape, no definite volume Gases Particles very far Least dense Most kinetic energy High amount of No definite shape or No organization o apart o o o motion o volume o gas liquid: condensation liquid gas: evaporating/vaporizing gas solid: deposition solid gas: sublimation 2. Boyle’s Law: if the temperature remains the same, pressure & volume are indirectly proportional. If one condition goes up, the other goes down & vice versa. P1V1 = P2V2 3. Charles’ Law: if the pressure remains constant, the temperature & volume are directly proportional. If one condition goes up, so does the other. V1 = V2 T1 T2 4. Gay Lussac’s Law: if the volume remains constant, the pressure & temperature are directly proportional – if one condition goes up, so does the other. P1 = P2 T1 T2 5. Combined Gas Law: shows the previous 3 gas laws in one. Only one found on the reference table. To use any of the 3 previous laws, simply eliminate the variable that remains constant. P1V1 = P2V2 T1 T2 May have to convert from grams to moles or vice versa depending on what the question gives/wants. where p is the pressure of the fluid V is the total volume of the container containing the fluid a is a measure of the attraction between the particles b is the volume excluded by a mole of particles n is the number of moles R is the universal gas constant.0821 Latm 8. Van der Waals Equation: This is the better version of the ideal gas law but requires a chart that would have to be given to use. Relating partial pressure to mole fraction 10.781 atm). Molar Mass: Rearranging the ideal gas law to find molar mass so 9.009 atm) & oxygen.4 LmmHg molK molK molK **Be careful to make sure the units cancel!!! 6. PV = nRT R is the gas law constant (there are 3 different ones you can used based on the unit the pressure is given in).6. So. Graham’s Law: Heavier gases travel slower than lighter gases (look at the molar masses to determine which is heavier).31 LkPa 62. 11. carbon dioxide (0. Gas Density: Rearranging the ideal gas law to find gas density so 8. You can determine how much faster using the following equation: √M2 / √M1 where M2 is the mass of the heavy gas & M1 is the mass of the light gas 7. T is the absolute temperature Practice Problems: 1. He was right.001 atm) argon (0. R= 0. Defining the RMS(root mean square) speed as a function of molar mass an temperature. what is the partial pressure of oxygen in atm if the total pressure is at STP (1 atm). Ideal Gas Law: Avogadro came along & said that perhaps the number of particles (atoms or molecules) in the gas sample may affect the three characteristics of gases. This is the way to find the average speed of particle such as a molecule or element in a gas. According to Dalton’s Law. What is the pressure in mmHg? . the number of moles (n) in the sample also has an effect. A gas mixture at STP includes nitrogen (0. All of these constants are given on the reference table. Calculate the number of liters occupied at STP by 6. The pressure of 3. CO2 or NH3 ? .2 L at a temperature of 350K with a pressure of 1.2 L at 80°C & at 200 kPa. 7.5 atm? 8. What is the pressure of 15 L of gas that was originally 75°C & 250 kPa & was changed to 50°C & 2. if the pressure remains constant? 5. What pressure will be exerted by 1. Which of the following behaves most like an ideal gas: He. If a sample of carbon dioxide occupies 5. what will be its new volume at 47°C.7 kPa of bromine.1L? 11. what will be its volume at STP? 6. 22. A mixture of a gas contains 50. If a sample of He gas occupies 12.5 L of nitrous oxide anesthetic gas is changed from 760 mmHg to 364 mmHg.45 moles of hydrogen gas at 25°C if the volume is 2.0 kPa of chlorine.5 mL? 9. What gas can travel faster – carbon dioxide or fluorine? How much faster will it travel? 10.8 moles of Kr. what will the resulting volume be? 4. Assuming the temperature remains constant. N2.3 kPa of He.2. How many moles of fluorine gas occupy 8. What is the total pressure of this deadly mixture? Is this at STP? 3.1 L at 332 °C. & 43.