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CHAPTERS 16-18,21, AND 22

CHAPTERS 16-18,21, AND 22. AP CHEMISTRY. FREE ENERGY CHANGE. G = G ° + RT In(P) ∆ G = ∆ G ° + RT In ( P p ) (P R )(P R ) ∆ G= ∆ G ° + RT In(Q) If G ∆ = 0 and Q = k, then ∆ G ° = -RTIn(k) Page 775 Table 16.6 ∆ G ° = ∆ H ° - T ∆ S °

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CHAPTERS 16-18,21, AND 22

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  1. CHAPTERS 16-18,21, AND 22 AP CHEMISTRY

  2. FREE ENERGY CHANGE • G = G°+ RT In(P) • ∆G = ∆G°+ RT In( Pp ) (PR)(PR) • ∆G= ∆G° + RT In(Q) • If G ∆ = 0 and Q = k, then ∆G ° = -RTIn(k) • Page 775 Table 16.6 • ∆G° = ∆H° - T∆S° • Remember S° is in J not in kJ

  3. CALCULATION OF ∆G FROM ∆G° • ∆G = ∆G° + RT In Q • Q = reaction quotient (section 15.5) • R= 8.314 J/Kmol • T = absolute temperature • -38kJ/mol • Example on page 776

  4. RELATION BETWEEN ∆G° AND k • ∆G° = -RTInk k = equilibrium constant • If k> 1, ∆G°< 0, spontaneous at standard conditions • If k<1, ∆G°>0, non-spontaneous at standard conditions • If k =1, ∆G°= 0, equilibrium at standard conditions

  5. REDOX • When oxidation number increases it is oxidized • When oxidation number decreases it is reduced • Substances that goes through oxidation are called the reducing agent • Substances that that goes through reduction are called the oxidizing agent • Balancing redox

  6. VOLTAIC CELLS • A spontaneous reaction used to produce electrical energy • Salt bridge cells • Zn(s) + Cu2+---> Zn2+(aq) + Cu(s) • Must design cells to make electron transfer occur indirectly

  7. Continue • Anode: Zn(s) --> Zn2+(aq) + 2e- • Cathode: Cu2+(aq) + 2e- --> Cu(s) • The salt bridge allows a current to flow, but prevents any contact between the zinc metal and copper (II) ions. This would short circuit the cell • Why?

  8. STANDARD VOLTAGE • E° Cell voltage when all the species are at standard concentration (1atm for gases, 1M for solutions in water) • E°cell = E°oxidation + E°reduction • Zn(s) + 2H+(aq, 1M) -->Zn2+(aq, 1M) + H2(g, 1 atm) • E° = +.0762V = E°oxZn + E°redH+ • Cu(s) --> Cu2+(aq) + 2e- • E°oxCu = -E°redCu2+ = -0.34 V • Relative strengths of oxidizing and reducing agents • The larger (more +) the value E°red, the stronger the oxidizing agent • The smaller the E°red (more -) the stronger the reducing agent

  9. Continue • Table 17.1 • Calculation of E° • E° = E°ox + E°red

  10. RELATION BETWEEN E, G, AND k • ∆G° = -n  E • lnk = n E°/0.0257 •  = 96.5 kJ/V mole of e- • If E° is positive, then ∆G° is negative • If lnk is positive, then k > 1 • Nernst equation • E = E° - (RT/n ) lnQ = E° - (0.0257/n)(lnQ) • When using Q remember that gases are entered as partial pressure in atm and solutes are concentrations (moles per liter)

  11. ELECTROLYTIC CELLS • Electrical energy supplied to bring abut a nonspontaneous redox reaction • Amount of products formed in electrolysis • Ag+ (aq) + e- --> Ag (s) • 1 mole of electrons = 96485 C = 1 mol Ag • # coulombs = # amperes X # of seconds • # Joules = # coulombs X # of volts

  12. Continue • Flow chart • Current and time --> quantity of charge in coulombs --> moles of electrons --> moles of elements --> grams of element • Commercial cells • Electrolysis of aqueous NaCl • 2H2O(l) + 2Cl-(aq) --> H2(g) +Cl2(g) + 2OH-(aq) • How much voltage is required

  13. LEAD STORAGE BATTERIES • Anode • Pb(s) + SO42-(aq) --> PbSO4(s) + 2e- • Cathode • PbO2(s) + 4H+(aq) + SO42-(aq) + 2e- --> PbSO4(s) + 2H2O(l) • Overall reaction • Pb(s) + 2SO42-(aq) +PbO2(s) +4H+(aq)-->2PbSO4(s) + 2H2O(l) • As the cell discharges, concentration of the sulfuric acid and the density of the battery will decrease

  14. RADIOACTIVE DECAY • Beta particles or β or e- • # of protons increase by one, mass stays constant • 146C --> 147N + 0-1e- • Zone of stability • Up to 83 • All nuclides with 84 or more protons are unstable • Small atoms that have a 1 to 1 ratio are stable. As they become larger more neutrons are needed to keep the protons in the nucleus (glue). After 84 no matter how many neutrons are used the nucleus will break apart

  15. Continue • Alpha particles or α or 42He2+ • Nuclides lose 2 protons and 2 neutrons. These particles are slower • 23090Th --> 42He2+ + 22688Ra • Gamma ray • High radiation with no loss of mass • 23892U --> 42He2+ + 23090Th + γ • Positron • Nuclides below the zone of stability (ratio is too small). • Same mass as an electron but opposite charge • Proton # decreases by one • 2211Na --> 01e + 2210Ne

  16. ELECTRON CAPTURE • Inner-orbital electron captured by the nucleus • 20180Hg + 0-1e- --> 20179Au + γ

  17. RATE OF DECAY • ln(N/No) = -kt N = # of nuclides • Half life t1/2 = 0.693/k • 1Ci = 3.700 X 1010 atoms/s

  18. Continue • Page 849 table 18.3 • Age of organic material; measure of C--14 content • 147N + 10n ---> 146C + 11H • 146C ---> 147N + 0-1β; t1/2 = 5720 yr • TABLE 18.5 radiotracers

  19. Continue • Mass defect = mass(n + p) - mass of nucleus • C-12: • Fission occurs with very heavy nuclei • Fusion occurs with light nuclei • Fission • 23592U + 10n --> 9037Rb + 14455Cs + 210n • Many different isotopes are formed

  20. Continue • More neutrons are produced than consumed, leading to a chain reaction. In nuclear reactors, excess neutrons are absorbed by cadmium rods • Nuclei produced have too many neutrons and hence are intensely radioactive. • 9037Rb --> 0-1e- + 9038Sr • This is the principal danger with nuclear reactors

  21. CHAPTER 21 • Colors of the ions • Pages 946, 951-955 • Oxidation states 952-954 • Vanadium has 4 states (common one 5+), manganese has 4 states, and nitrogen has 5 states • Coordination #’s pages 955-959 • Coordination numbers and ligands 956-960 • Optical isomerism page 961-965 • Chiral 964 • Go over page 968 • Read and take notes 965 to end of chapter

  22. CHAPTER 22 • Go over table 22.1 • Exercise 22.3 • Exercise 22.4 • Exercise 22.5 • Read and take notes 1008 to end of chapter

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