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

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

3. Clicker Question Use the following data for methanol (CH3OH):
ΔHvaporization = 35.3 kJ/mol at 64.7°C
Determine ΔE (kJ/mol) for methanol vaporizing at 64.7°C.
a) b) c) –35.3 d) e) –38.1

4. Determining Hrxn
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. Bomb Calorimeter (constant V)

7. NH4NO3(s)  NH4+(aq) + NO3–(aq) ΔH = 25.7 kJ
Clicker Question
A g sample of NH4NO3(s) is dissolved in mL of water with both substances initially at room temperature (24.7°C). Calculate the final temperature of the solution. You may make the following assumptions: no heat loss to the surroundings; the specific heat capacity of the solution is 4.18 J/g°C; and the density of water is 1.00 g/mL.
NH4NO3(s)  NH4+(aq) + NO3–(aq) ΔH = 25.7 kJ
a) 17.0°C
b) 17.7°C
c) 31.7°C
d) 32.4°C
e) I cannot get any of these answers.