University:
Felician University
Course:
PHYS-355 | Advanced Topics in Physics
Academic year:

2020
Views:

264

Pages:

18
Author:

StellarSymphony

Gas Laws Introduction to Gas Laws • Gases are important substances in chemistry, they have many important properties that is important to understand • We will be learning about four gas laws: 1. Boyle’s Law 2. Charles’ Law 3. Gay-Lussac’s Law 4. Ideal Gas Law What is Pressure? • A type of physical force acting on an object • SI Units: Pascals (Pa) or Kilopascals (KPa) • Older units: torr = 1 mm of Hg • STP (Standard Temperature & Pressure) = 760 mmHg = 760 torr = 1 atm = 100.3 KPa What is Temperature? • The amount of heat in a substance • Normally in degrees Celsius, but you may have to convert to Kelvin • 0 Kelvin = -273.15 oC • Convert K → oC (add (+) 273.15) • Concert oC → K (minus (-) 273.15) [ºC] = [K] – 273.15 Examples: 350K = ______ oC 35 oC = ______ K Boyle’s Law • If you decrease the volume of a gas, the pressure will go up. • If you increase the volume of a gas, the pressure will go down Boyle’s Law • The relationship of pressure & volume of gasses Volume L Pressure P1V1=P2V2 Atm or kPA Charles’ Law • If you increase the temperature of a gas, the volume will go up. • If you decrease the temperature of a gas, the volume will go down Charles’ Law • The relationship of temperature & volume of gases Temperature K or oC Volume L Gay-Lussac’s Law • If you increase the temperature of a gas, the pressure will go up. • If you decrease the temperature of a gas, the pressure will go down Gay-Lussac’s Law • The relationship of temperature & pressure of gases Temperature K or oC Pressure Atm or kPA *Avogadro’s Law • P, V, and T are not the only factors that affect gases though. Avogadro’s hypothesis states: "equal volumes of all gases, at the same temperature and pressure, have the same number of particles" • There is one more gas variable: n, which stands for the number of moles. • The second part of Avogadro’s hypothesis states that For a given mass of an ideal gas, the moles and volume are directly proportional if the temperature and pressure are constant. V n = d or V1 n1 = V2 n2 Combined Gas Law • Take the formulas given from Boyle’s Law, Charles’ Law, GayLussac’s Law & Avogadro's Law & write a combined gas law • Your combined gas law should include volume, temperature & pressure PV =R nT or PV= nRT R is a constant. R changes depending on the units for P. Here are common values of R. You do NOT need to memorize these numbers, they will be given to you on tests and quizzes. • R = 8.314 L∙kPa K∙mol R=0.082057 • The formula you need to know for a test!!!!! L∙atm K∙mol Practice Problem 1 Using the ideal gas law, PV= nRT, we can find out where the number STP for liters came from n = 1.00 mole, R = .0821 L atm/mole k, P = 1.00 atm, T = 273.15K, PV=nRT 1.00 atm x V=(1.00 mol x .0821 L • atm/mole•k x 273.15K) V=(1.00 mol x .0821 L • atm/mole•k x 273.15K) 1.00 atm V= 22.4 L Practice Problem 2 At what temperature will 0.654 moles of neon gas occupy 12.30 liters at 1.95 atmospheres? PV=nRT 1.95 atm x 12.30L=(0.654 mol x .0821 L•atm/mole•k x T) 1.95 atm x 12.30L =T 0.654 mol x .0821L • atm/mole•k 447 K=T Practice Problem 3 Find the number of moles of xenon gas that is present in a 5.00L container with a pressure of 58.6 kPa and temperature of 60.0ºC. [ºC] = [K] – 273.15 60.0ºC= [K] – 273.15 333.15=[K] PV=nRT 58.6kPa x 5.00L=n x 8.314L • kPa/mole•k x 333.15K 58.6kPa 5.00 =n 8.314L • kPa/mole•k x 333.15K x L 0.106 mol = n