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Bell Work

Bell Work. Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values: 2 SO 2 (g) + 2 P(s) + 5 Cl 2 (g )  2 SOCl 2 (l) + 2 POCl 3 (l)

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Bell Work

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  1. Bell Work Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values: 2 SO2(g) + 2 P(s) + 5 Cl2(g) 2 SOCl2(l) + 2 POCl3(l) SOCl2(l) + H2O(l) SO2(g) + 2 HCl(g) ΔHo/kJ = +10.3PCl3(l) + 1/2 O2(g)POCl3(l) ΔHo/kJ = -325.7P(s) + 3/2 Cl2(g)PCl3(l) ΔHo/kJ = -306.74 HCl(g) + O2(g)2 Cl2(g) + 2 H2O(l) ΔHo/kJ = -202.6 What is the change in temperature, if 3450J of heat are added to a 23.4 gram sample of Fe. (Specific heat of iron is 0.444 J/g0C

  2. Gases Chapter 13

  3. Properties • Uniformly fills a container • Easy to compress • Mixes completely with other gases • Exerts pressure on surroundings • Atmospheric pressure results from the mass of the air being pulled toward the center of the earth by gravity---weight of the air.

  4. Units of pressure • mmHg (millimeters of mercury) • Torr • Torr and mmHg can be used interchangeably • Atm (standard atmosphere) • Pascal

  5. Kinetic-Molecular theory • Gases can be compressed easily, but liquids and solids cannot be compressed because particles are already close together • The intermolecular forces between gases are weak. • Gas particles move until a collision alters their course • Energy added into the system increases the kinetic energy of the particles, which translates to an increase in temperature of the gas.

  6. Relationship between pressure and volume • Boyle’s law- pressure times volume equals a constant • P1V1=P2V2

  7. Example of Boyle’s Law • A container holds 500. mL of CO2 at 20.° C and 742 torr. What will be the volume of the CO2 if the pressure is increased to 795 torr? • V1=500mL • P1=742 torr • V2= x • P2=795 torr • (500mL)(742Torr)=(x)(795Torr) • X=470mL

  8. Practice Problem • A gas tank holds 2785 L of propane, C3H8, at 830. mm Hg. What is the volume of the propane at standard pressure, 760mmHg? V1P1 = V2P2 (2785L)(830mmHg)=(x)(760mmHg) 3042L

  9. Relationship between volume and temperature • Charles’s Law-gas volume is directly proportional to the temperature • V1 = V2 T1 T2 • Temperature is in Kelvin(+273)

  10. Example of Charles’s Law • A container holds 50.0 mL of nitrogen at 25° C and a pressure of 736 mm Hg. What will its volume be, if the temperature increases by 35° C? V1 = V2 T1T2 50mL = x 298K 333K x= 56mL

  11. Practice problem • A sample of helium has a volume of 521 dm3 at a pressure of 75 cm Hg and a temperature of 18° C. When the temperature is increased to 23° C, what is the volume of the helium? V1 = V2 T1T2 521dm3 = x 291K 296K =530dm3

  12. Combined gas Law • P1V1 = P2V2 T1 T2 • The combined gas law is a mix between Charles’s, Boyle’s, and Gay-Lussac’s Laws

  13. Example • A sample of argon has a volume of 5.0 dm3 and the pressure is 0.92 atm. If the final temperature is 30.° C, the final volume is 5.7 L, and the final pressure is 800. mm Hg, what was the initial temperature of the argon? P1V1= P2V2 T1 T2 (5.0dm3)(0.92atm) = (5.7L)(1.05atm) x 303K =233K

  14. Practice problem • A sample of sulfur dioxide occupies a volume of 652 mL at 40.° C and 720 mm Hg. What volume will the sulfur dioxide occupy at STP? P1V1= P2V2 T1T2 (652mL)(720mmHg) = (x)(760mmHg) 313K 273K 539mL

  15. Avogadro’s Law • States that the volume of gas is proportional to the number of gas particles at constant temperature and pressure. • I.E. A volume occupied by one mole of gas is 22.4L when the temperature of the gas is at 0oC and its pressure is at 1atm. • These conditions are referred to as standard temperature and pressure (STP)

  16. STP conditionsstandards listed below • 22.4 Liters • 1 atm=760mmHg or Torr • 273 K

  17. Example of STP • Calculate the number of moles of nitrogen gas produced and grams of sodium azide consumed if 115L of N2 results from a sodium azide explosion. 115L x 1mol 22.4L =5.13 moles

  18. Ideal gas Law • PV=nRT • P-pressure(atm) • V-volume(L) • n-number of moles (mol) • R-constant (0.0821L*atm/mol *K) • T-temperature (Kelvin)

  19. Example • A reaction yields 3.75 L of nitrogen monoxide. The volume is measured at 19°C and at a pressure of 1.10 atm. What mass of NO was produced by the reaction? PV=nRT (1.10atm)(3.75L) =x(0.0821L*atm/mol*K)(292K) 0.17moles 0.17mol x 30g/mol 5.1 g

  20. Practice problem • What is the pressure inside a tank that has a volume of 1.20 x 103L and contains 12.0 kg of HCl gas at a temperature of 18°C? PV=nRT (x)(1.20x103L)=(329mol)(0.0821L*atm/mol*K)(291K) 6.6atm

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