1. Relating energy and extent of reaction

2.  Define thermodynamics  Define enthalpy  How is enthalpy related to the first law of thermodynamics?

3.  Why can we not use the value ∆E to tell us whether or not a process is favored?  Define spontaneous and non- spontaneous reactions.  GENERALLY SPEAKING: processes that are spontaneous in one direction are non- spontaneous in another

4.  Predict which experimental conditions are important in determining spontaneity of reaction.  Temperature: IE: Ice Melting  at -10 degrees Celsius, water freezes spontaneously  Pressure:  NOTE: A spontaneous reaction can be very fast or very slow. Thermodynamics tells us direction and extent but not speed.

5.  Predict whether or not each process is spontaneous as described, spontaneous in reverse, or in equilibrium. Water at forty degrees Celsius gets hotter when a piece of metal heated to one hundred and fifty degrees Celsius is added Water at room temperature decomposes into hydrogen and oxygen gas Benzene vapor at a pressure of 1 atm condenses to liquid benzene at the normal boiling point of benzene  At 1 atm pressure, solid carbon dioxide sublimes at -78 degrees Celsius. Is this process spontaneous at -100 degrees Celsius?

6.  Ideal Engine: Sadi Carnot- analyzed factors that determine how efficiently a steam engine can convert heat to work  Impossible to convert energy content of a fuel completely to work- Why? Ideal engines operates under ideal set of conditions in which all processes are reversible.  Define Reversible Process  Define Irreversible Process Reversible change produces the maximum amount of work that can be done by a system on its surroudings

7.  Predict if flow of heat is a reversible process. Justify your reasoning.  Reversible Processes are those that reverse direction whenever an infinitesimal change is made in some property of the system

8.  Define Isothermal  Suppose an ideal gas is confined to ½ a cylinder with a removable piston. The partition is removed and the gas expands. Is this process reversible?  The path that restores the system to its original state requires a different value of w than the original path. The same path can’t be followed- thus it is irreversible.

9.  ALL REAL PROCESSES ARE IRREVERSIBLE  A NONSPONTANEOUS PROCESS CAN ONLY OCCUR IF THE SURROUNDINGS DO WORK ON THE SYSTEM.  ANY SPONTANEOUS PROCESS IS IRREVERSIBLE

11.  DO NOW: AP Practice Question: Lewis Structures and PE Diagrams

12. Please take out homework and compare answers with your neighbor.

13.  Any irreversible process results in an increase in total entropy, whereas any reversible process results in no overall change in entropy. Irreversible Process: ∆S univ = ∆S sys + ∆S surr > 0 Reversible Process: ∆S univ = ∆S sys + ∆S surr = 0 Entropy of the universe increases in any spontaneous process!!

14.  On the molecular level, how are molecules affected when a substance is heated?  Types of molecule movement: Translational Motion: movement in one direction. Vibrational Motion: atoms within molecule move periodically toward and away from one another. Rotational Motion: molecules spin on an axis  Different forms of motion are ways in which molecule can store energy (AKA motional energy)

15.  Compare and contrast the possible motions of atoms to those of molecules.  Number of microstates possible for a system increases with: increase in temperature, increase in number of molecules. Any of changes increase possible positions and KE of molecules in system.

16.  ENTROPY IS: RANDOMNESS OR DISORDER OF SYSTEM DISPERSION OF ENERGY

17.  Based on the images above and your knowledge of entropy, explain the differences in entropy of the different states of water.

18.  2 examples: How does the entropy of the system change when an ionic solid is dissolved in water? Chemical Reactions:  2 NO(g) + O 2 (g)  2 NO 2 (g)

19.  We generally expect entropy of a system to increase for processes in which: Gases form from either solids or liquids Liquids or solutions form from solids Number of gas molecules increases during a chemical reaction

20.  Predict whether ∆S is a positive or negative for each process (assuming constant Temp) Liquid water becomes water vapor Silver and Chlorine ions form Silver Chloride Solid Iron is oxidized to form Fe 2 O 3 Nitrogen and Oxygen gases form NO gas.

21.  In each pair, choose the system that has the greater entropy and explain your choice 1 mol of NaCl(s) or 1 mol of HCl(g) 2 mol of HCl(g) or 1 mol of HCl(g) 1 mol of HCl(g) or 1 mol of Ar(g)

22.  As we reach absolute zero, predict what will happen to the entropy of the system?  Entropy of a pure crystalline substance at absolute zero is zero: S(0 K) = 0.

23.  No finite method of measuring ∆S for a reaction Since third law establishes a zero point, experimental measurements can determine absolute value of the entropy

24.  Molar entropies for substances in their standard states are known as standard molar entropies and denoted as S°  With a partner, make observations based on the table.

25. DO NOW: Calculate the standard entropy of the system, ∆S°, for the Haber Process.

26.  How do we determine the spontaneity of a reaction?  Spontaneity is based off of 2 concepts- enthalpy and entropy.  What does this suggest for our aim?

27.  Predict how we would calculate the change in entropy in the surroundings.  How would we calculate the enthalpy change for the system?  Why is the positive value for entropy of the surroundings expected?

28.  Josiah Willard Gibbs American Mathematician (1839-1903) First person to be awarded a Ph.D. in science from an American university  New State Function: Gibbs free energy (G) G = H – TS T = absolute temperature

29.  For an isothermal process, how would we represent the change in the free energy of a system?  How can we derive our equation for an isothermal and isobaric reaction?  What information does the value of G give us?

30.  If both T and P are constant ∆G < 0, reaction is spontaneous in forward direction ∆G = 0, reaction is at equilibrium ∆G > 0, reaction is spontaneous in reverse direction  Why is using ∆G as a criterion for spontaneity better than using entropy?  IN ANY SPONTANEOUS PROCESS CARRIED OUT AT CONSTANT PRESSURE AND TEMPERATURE, FREE ENERGY ALWAYS DECREASES.

31.  Calculate the standard free-energy change for the formation of NO from N 2 and O 2 at 298 K. ∆H°=180.7 kJ ∆S°= 24.7 J/K  Is this reaction spontaneous?

32.  Why can’t we use the Δ G° from appendix C to calculate all reactions?  Lets consider the melting of ice: H2O (s)  H2O (l) Predict the sign of H and S Generally, H and S values don’t vary much with temperature. How does the G change?

34.  Most chemical reactions occur under nonstandard conditions  ∆G= ∆G° + RT lnQ R = ideal gas constant T = absolute temp Q= reaction quotient (Chapter 15) (Q=1 @ standard conditions)  At standard conditions, ∆G= ?

35.  Using the previous equation, determine the equation to0 solve for K.  ALWAYS BEWARE UNITS.  If ∆G° is negative, K > 1  If ∆G° is positive, K<1.