1. © University of South Carolina Board of Trustees Chapt. 17 Thermodynamics Overview

2. © University of South Carolina Board of Trustees Re-Read Chapt. 5 Especially: ●System vs Surroundings ●Thermodynamic State and State Functions ●Enthalpy and Hess’ Law ●Heat and Heat Capacity ●Calorimetry (at constant pressure)

3. © University of South Carolina Board of Trustees Overview Energy (  E = w + q ) ●work ( w ) ●heat ( q ) Enthalpy (  H =  E + P  V) Entropy ( S ) Gibb Free Energy ( G )  G =  H - T  S K eq = exp(-  G / RT )

4. © University of South Carolina Board of Trustees Chapt. 17 Thermodynamics Sec. 1 Work and Heat

5. © University of South Carolina Board of Trustees Work vs Heat Both: ●are a transfer of energy between system and surroundings ●are positive for energy going into the system (negative out of the system) Work ( w ) is a transfer of ordered energy Heat ( q ) is a transfer of disordered energy

6. © University of South Carolina Board of Trustees Work - General Special cases of work: ●Electric current (force from voltage on electrons) ●Raising a weight (force from gravitation) ­Expansion and Compression  w = F orce x d istance

7. © University of South Carolina Board of Trustees Work of Expansion/Compression P = external Pressure V = Volume  V = V final - V initial 1 L·atm = 101.3 J w = - P ex  V

8. © University of South Carolina Board of Trustees Example: Expansion Work An ideal gas has a volume of 20.0 L and a pressure of 12.0 atm. It expands against a constant pressure of 1.5 atm until the gas equilibrates with the external pressure. The temperature is constant during the expansion. What is the work done?

9. © University of South Carolina Board of Trustees P - V Work in Chemical Reactions 2H 3 O + (aq) + Zn (s)  H 2(g) + Zn 2+ (aq) + 2H 2 O (l) 2O 3(g)  3O 2(g) ●Liquids and solids have negligible volume ●Gas volume from ideal gas equation V (g) = n (g) RT / P  V (rxn)  V (g) =  n (g) RT / P

10. © University of South Carolina Board of Trustees Example: Work in a Reaction How much work is done when 0.50 mole of Zn is dissolved in an HCl solution at 25 °C? 2H 3 O + (aq) + Zn (s)  H 2(g) + Zn 2+ (aq) + 2H 2 O (l)

11. © University of South Carolina Board of Trustees Heat vs Temperature (Chapt. 5) q = heat C = heat capacity  T = T final - T inital 1 cal = 4.184 J(1 Cal = 1 kcal = 10 3 cal) q = C  T

12. © University of South Carolina Board of Trustees Chapt. 17 Thermodynamics Sec. 2 1 st Law

13. © University of South Carolina Board of Trustees 1 st Law of Thermodynamics ●Energy is neither created nor destroyed. (It can be transferred or change form.) ●The energy of an isolated system is constant. ●In a non-isolated system, the energy only changes because of energy transfers with the surroundings.  E = q + w