1. TUESDAY, JANUARY 5TH Take out review questions 13-25 and problem set 3 Today’s agenda 19.5-19.7 overview Work time for problem set 4 and cumulative questions Tomorrow at the start of class is the deadline to get homework checked! Ch 5 tests back

2. YAY! Tomorrow we will go get our new textbooks!!!!!!!!!!! Bring your school ID *Technically* you’re supposed to turn in your old book tomorrow, however, you won’t be charged for it until the end of the year. So if you’re really attached, keep it We will start our next chapter out of the new book Soon I will be able to give you online access to the book/online homework system – still working on getting access codes from the district

3. CALCULATING  G  At 25 °C At temperatures other than 25  C Assuming the change in  H o reaction and  S o reaction is negligible Or

4. ΔG° AND PREDICTING SPONTANEITY Recall that reactions tend towards spontaneity IF ΔH < 0 (exothermic) ΔS > 0 (increase in entropy) ΔG° = ΔH – TΔS Sign of ΔHSign of ΔSSpontaneity -+ +- -- ++

5. STANDARD FREE ENERGIES OF FORMATION The free energy of formation (  G f °) is the change in free energy when 1 mol of a compound forms from its constituent elements in their standard states. The free energy of formation of pure elements in their standard states is zero. Insert Table 17.3

6.  G RELATIONSHIPS If a reaction can be expressed as a series of reactions, the sum of the  G values of the individual reactions is the  G of the total reaction.  G is a state function. If a reaction is reversed, the sign of its  G value reverses. If the amount of materials is multiplied by a factor, the value of the  G is multiplied by the same factor. The value of  G of a reaction is extensive.

7. WHAT’S “FREE” ABOUT FREE ENERGY? The free energy is the maximum amount of energy released from a system that is available to do work on the surroundings. For many exothermic reactions, some of the heat released due to the enthalpy change goes into increasing the entropy of the surroundings, so it is not available to do work. And even some of this free energy is generally lost to heating up the surroundings.

8.  G UNDER NONSTANDARD CONDITIONS   G =  G  only when the reactants and products are in their standard states. Their normal state at that temperature Partial pressure of gas = 1 atm Concentration = 1 M  Under nonstandard conditions,  G =  G  + RTlnQ. Q is the reaction quotient.  At equilibrium,  G = 0.  G  = −RTlnK

9.  Gº AND K Because  G rxn = 0 at equilibrium, then  Gº = −RTln(K) When K < 1,  Gº is positive and the reaction is spontaneous in the reverse direction under standard conditions. Nothing will happen if there are no products yet! When K > 1,  Gº is negative and the reaction is spontaneous in the forward direction under standard conditions. When K = 1,  Gº is 0 and the reaction is at equilibrium under standard conditions.

10. ANNOUNCEMENTS All homework due tomorrow at the start of class Tomorrow’s agenda Check homework Get books Question time for all of chapter 19 (review questions, problem sets, cumulative questions) Ch 19 test this Thursday! Ch 5 and 17 retake deadline is next Thursday Work back