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

2. Clicker Question
Determine the signs of ΔH, ΔS and ΔG for the freezing of liquid water at 2°C and 1 atm.
ΔH ΔS ΔG
a) – – –
b) – – + c)
d) + – 0
e) – + 0

3. Clicker Question
For the melting of ice at 10°C and 1 atm what are the signs for ∆H, ∆S, and ∆G?
ΔH ΔS ΔG
a) + – 0
b) – + 0 c)
d) + + –
e) – + –

4. Clicker Question
Each of the following chemical reactions represented below is spontaneous at some temperature:
I. 2KClO3(s)  2KCl(s) + 3O2(g)
II. 2H2O2(l)  2H2O(l) + O2(g)
III. Pb(NO3)2(aq) + 2NaCl(aq)  PbCl2(s) + 2NaNO3(aq)
IV. 2SO3(g)  2SO2(g) + O2(g)
From just this fact (that each is spontaneous) and the balanced chemical equations, how many of the reactions can you conclude must be exothermic? Note: do not use any background knowledge about the reactions (that is, the question is not asking which are actually exothermic but which must be exothermic given the information provided).
a) b) 1 c) d) 3 e) 4

5. Determining Grxn
Consider the following reaction at constant temperature and pressure:
2CO(g) + O2(g)  2CO2(g)
Consider:
1. Predict if S° is positive or negative (we will determine it next).
2. Predict if the reaction is exothermic or endothermic (we will determine it next).
3. Can we predict the sign of G°?
4. At what temperatures is this reaction spontaneous?

6. Determining Grxn 2CO(g) + O2(g)  2CO2(g) G (kJ/mol) -137 0 -394
H (kJ/mol)
S (J/Kmol)
Consider:
1. Determine S° (check prediction).
2. Determine H° (check prediction).
3. Determine G° two ways.
4. At what temperatures is this reaction spontaneous?