1 / 11

February 5, 2008

February 5, 2008. Go over Charles’s Law and Avogadro’s Law Homework Introduce Combined Gas Law Introduce Ideal Gas Law Work Sample Problems HOMEWORK: Pg. 480 -- #21, 23ac, 24ac, 25, 28, 29. Equation of State of an Ideal Gas. Robert Boyle ( 1662 ) found that at fixed temperature

elvis-gilbert
Download Presentation

February 5, 2008

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. February 5, 2008 • Go over Charles’s Law and Avogadro’s Law Homework • Introduce Combined Gas Law • Introduce Ideal Gas Law • Work Sample Problems • HOMEWORK: Pg. 480 -- #21, 23ac, 24ac, 25, 28, 29

  2. Equation of State of an Ideal Gas • Robert Boyle (1662) found that at fixed temperature • Pressure and volume of a gas is inversely proportional PV = constant Boyle’s Law • J. Charles found that at fixed pressure • Volume of gas is proportional to change in temperature He Volume CH4 H2O H2 -273.15 oC Temp All gases extrapolate to zero volume at a temperature corresponding to –273.15 oC (absolute zero).

  3. Kelvin Temperature Scale • Kelvin temperature (K) is given by K = oC + 273.15 where K is the temperature in Kelvins, oC is temperature in Celsius • Using the ABSOLUTE scale, it is now possible to write Charles’ Law as V / T = constant Charles’ Law • Combining Boyle’s law, Charles’ law, and another law called Gay-Lussac’s Law (relating pressure and temperature) we can mathematically prove that P V / T = constant Charles

  4. Combined Gas Law • This brings us to the combined gas law:

  5. Practice Problem • A 1.50 L sample of neon gas at 1.10 atm and 25 °C is heated to 45 °C. The neon gas is the subjected to a pressure of 1.50 atm. Determine the new volume of the neon gas. P1 = 1.10 atm V1 = 1.50 L T1 = 25 °C = 298 K P2 = 1.50 atm V1 = ???? L T1 = 45 °C = 318 K V2 = 1.17 L

  6. The Combined Gas Law When measured at STP, a quantity of gas has a volume of 500 cm3. What volume will it occupy at 0 oC and 93.3 kPa? (101.3 kPa) x (500 cm3) = (93.3 kPa) x (V2) 273 K 273 K P1 = 101.3 kPa T1 = 273 K V1 = 500 cm3 P2 = 93.3 kPa T2 = 0 oC + 273 = 273 K V2 = X cm3 V2 = 542.9 cm3

  7. Ideal vs. Real Gases No gas is ideal. Most gases behave ideally (almost) at pressures of approximately 1 atm or lower, when the temperature is approximately 0 °C or higher. When we do calculations, we will assume our gases are behaving as ideal gases

  8. Ideal Gas Equation Universal Gas Constant Volume PV = nRT Pressure Temperature No. of moles R = 0.0821 atm L / mol K R = 8.314 kPa L / mol K Kelter, Carr, Scott, Chemistry A Wolrd of Choices 1999, page 366

  9. nRT V = P (500 g)(0.0821 atm . L / mol . K)(300oC) = V 740 mm Hg Ideal Gas Law What is the volume that 500 g of iodine will occupy under the conditions: Temp = 300oC and Pressure = 740 mm Hg? Step 1) Write down given information. mass = 500 g iodine T = 300oC P = 740 mm Hg R = 0.0821 atm . L / mol . K Step 2) Equation: PV = nRT Step 3) Solve for variable Step 4) Substitute in numbers and solve V = What MISTAKES did we make in this problem?

  10. What mistakes did we make in this problem? What is the volume that 500 g of iodine will occupy under the conditions: Temp = 300oC and Pressure = 740 mm Hg? Step 1) Write down given information. mass = 500 g iodine Convert mass to moles; recall iodine is diatomic (I2) 500 g I(1 mole I2/254 g I2) n = 1.9685 mol I2 T = 300oC Temperature must be converted to Kelvin T = 300oC + 273 T = 573 K P = 740 mm Hg Pressure needs to have same unit as R; therefore, convert pressure from mm Hg to atm. x atm = 740 mm Hg (1 atm / 760 mm Hg) P = 0.8 atm R = 0.0821 atm . L / mol . K

  11. nRT V = P (1.9685 mol)(0.0821 atm . L / mol . K)(573 K) = V 0.9737 atm Ideal Gas Law What is the volume that 500 g of iodine will occupy under the conditions: Temp = 300oC and Pressure = 740 mm Hg? Step 1) Write down given information. mass = 500 g iodine n = 1.9685 mol I2 T =573 K (300oC) P =0.9737 atm(740 mm Hg) R = 0.0821 atm . L / mol . K V = ? L Step 2) Equation: PV = nRT Step 3) Solve for variable Step 4) Substitute in numbers and solve V = 95.1 L I2

More Related