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Announcements

Announcements. To join clicker to class today: Turn on the Clicker (the red LED comes on). Push “Join” button followed by “20” followed by the “Send” button (switches to flashing green LED if successful). Exam 4 on Chapters 7 & 8 next Wednesday.

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Announcements

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  1. Announcements • To join clicker to class today: • Turn on the Clicker (the red LED comes on). • Push “Join” button followed by “20” followed by the “Send” button (switches to flashing green LED if successful). • Exam 4 on Chapters 7 & 8 next Wednesday. • All study material for these chapters is posted on web site. • Do not forget about the Lewis Tutorial, the VSEPR examples on Web site and the text site as well for more examples and pictures. • Quiz Monday on 8.1-8.7.

  2. Review • PV = nRT • Solved for P = nRT/V • Solved for V = nRT/P • Solved for n = PV/(RT) • Solved of T = PV/(nR) • Partial pressures • Ptot = P1 + P2 + … = (n1 + n2 + …)RT/V • Pi = XiPtot • ∑i Xi = 1 or X1 + X2 + X3+ ... = 1 • Example of finding volume that would be occupied by one of the gases in a mixture.

  3. Dalton’s Law to find volume contributed by a gas. • PV = nRT & Ptot = (n1+n2+..)RT • Calculated @60˚C PH2O = 0.20 atm, if Ptot = 1.00 atm => PN2 = 1.00 – 0.20 = 0.80 atm. • Given total V = 0.045 L calculated nN2=PN2Vtot/RT=1.3 x 10-3 mol N2. • If there had been no water vapor than PN2 = 1.00 atm. Used this to calculate VN2 = nN2RT/Ptot = 36. mL.) • Can be shorter if do it symbolicly first. Final equation: VN2 = PN2Vtot/Ptot = (0.80 atm)(45 mL)/(1.00 atm)= 36. mL!

  4. Henry’s Law of Gas Solubility • Cgas = kHPgas • Cgas = molarity of gas in solution • kH = the Henry’s law constant for a particular gas in a particular solvent • Pgas = the partial pressure of the gas • This law is an empirical observation.

  5. Kinetic Molecular Theory of Gases • Molecules assumed to be very small (essentially points with no volume) • They are constantly moving and exchanging kinetic energy through elastic collisions => they are changing direction and speed randomly, but total kinetic energy constant. • Pressure = sum of the force of many collisions with the walls of the container. • Based on KE = (1/2)mu2 (u = speed). • Key result: urms = (3RT/M)1/2

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