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Ideal Gas Law & Gas Stoichiometry

Ideal Gas Law & Gas Stoichiometry. Ideal Gas Law. P V = n R T P = Pressure ( atm ) V = Volume (L) T = Temperature (K) n = number of moles R = 0.0821 L atm / mol K. THIS EQUATION ONLY WORKS IF ALL MEASUREMENTS ARE IN THE CORRECT UNITS!. PV = nRT.

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Ideal Gas Law & Gas Stoichiometry

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  1. Ideal Gas Law & Gas Stoichiometry

  2. Ideal Gas Law P V = n R T • P = Pressure (atm) • V = Volume (L) • T = Temperature (K) • n = number of moles • R = 0.0821 L atm / mol K THIS EQUATION ONLY WORKS IF ALL MEASUREMENTS ARE IN THE CORRECT UNITS!

  3. PV = nRT • Calculate the number of moles of a gas contained in a 3.0 L vessel at 300.0K with a pressure of 1.50 atm

  4. Example Dinitrogen monoxide (N2O), laughing gas, is used by dentists as an anesthetic. If 2.86 mol of gas occupies a 20.0 L tank at 23°C, what is the pressure (mmHg) in the tank in the dentist office? Note: 1atm = 760 mm Hg

  5. Avogadro’s Principle • AP– equal volumes of gases at equal temperature and pressure contain the same number of particles • Molar volume – the volume of gas that 1 mole of a substance occupies at STP • At STP, the volume of 1 mol of a gas = 22.4 L • New conversion factor at STP ONLY! 1 mol 22.4 L

  6. Example • Calculate the volume 0.881 mol of a gas will occupy at STP.

  7. Example • Calculate the volume that 2.000 kg of methane would occupy at STP.

  8. Gas Stoichiometry • 2C4H10 + 13O2 8 CO2 + 10 H2O • Just like a mole to mole ratio, you can now have a liter to liter ratio

  9. Example • C3H8 + 5O2 3CO2 + 4 H2O • What volume of oxygen gas is needed for the complete combustion of 4.00 L C3H8?

  10. Another Example • How many g of CaH2 are required to generate 25.0 L of H2 at STP? • CaH2 + 2H2O  Ca(OH)2 + 2H2

  11. Example • N2 + 3H2 2NH3 • If 5.00 L of N2 react completely at 3.00 atm and 298 K, how many grams of ammonia are produced? • You cannot use straight stoichiometry, but you can go from L of one thing to L of another any time

  12. Dalton’s Law of Partial Pressure • The pressure of a mixture of gases is equal to the sum of the partial pressures of each gas in the mixture PTotal = P1 + P2 + P3 + …….

  13. Example • A gaseous mixture is made from 6.00 g O2 and 9.00 g CH4 in a 15.0 L vessel at 273 K. What is the partial pressure of each gas?

  14. Example What would be the total pressure?

  15. Try this example • What is the total pressure exerted by a mixture of 2.00 g of hydrogen gas and 8.00 g of nitrogen gas at 273 K in a 10.0 L vessel?

  16. Collecting Gases Over Water • In chemistry it is often necessary to determine the number of moles of a gas generated in a chemical reaction. • We do this by water displacement

  17. Total Pressure • P T = P gas + P water vapor • The pressure of the water vapor can be looked up in a chart in appendix B

  18. Example • A sample of KClO3 is partially decomposed producing oxygen gas that is collected over water. The total volume of gas that is collected is 0.250 L at 26°C and 765 torr (1atm = 760 torr) • Question #1 • How many moles of oxygen were collected?

  19. Question # 2 • Calculate the number of grams of KClO3 that were actually decomposed

  20. Another Example • NH4NO2 N2 + 2H2O • A sample of ammonium nitrite is decomposed and 511 ml of gas are collected over water at 26°C and 745 torr of total pressure. How many grams of ammonium nitrite were decomposed?

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