As always… n n n Lon-Capa assignments Lecture videos Textbook n n Read Do text homework 1

Office Hours 3014 Chemistry Annex n [email protected] edu n 11 am-12 pm Mondays and Wednesdays (after lecture) n 10 -11 am Tuesdays and 1 -2 pm Thursdays n By appointment; open-door policy n 22

Clicker Question Calculate E for a system that releases 28 J of heat while 63 J of work is done on it. a) b) c) d) -35 J -91 J 35 J 91 J 3

Clicker Question Use the following data for methanol (CH 3 OH): ΔHvaporization = 35. 3 k. J/mol at 64. 7°C Determine ΔE (k. J/mol) for methanol vaporizing at 64. 7°C. a) 32. 5 b) 35. 3 c) – 35. 3 d) 38. 1 e) – 38. 1 4

Determining Hrxn n Since H = qp, determine the heat given off or required at constant pressure by measuring temperatures. This is termed calorimetry. Since energy is conserved, we can often determine Hrxn for one reaction given values of Hrxn for others. Uses the principle in Hess’s Law. Use standard enthalpies of formations for reactants and products (we have tables of these). 5

A Coffee. Cup Calorimeter Made of Two Styrofoam Cups 6

Clicker Question A 25. 0 g sample of copper (c= 0. 385 J/g C) is placed in a boiling water bath until the temperature of the metal is 100. 0 C. The metal is quickly transferred to 100. 0 g of water at 25. 0 C in a calorimeter (specific heat capacity of water = 4. 18 J/g C). Determine the final temperature of the water in the calorimeter. a) b) c) d) e) 22. 2°C 23. 2°C 25. 9°C 26. 7°C 27. 8°C 7