General Chemistry II
Recitation Worksheet #8
CHEM 1018
Name:_________________________
Date:_________________________
1. Determine whether the entropy changes for the following transformations is positive or negative.
a. KClO3 (s) → 2 KCl (s) + 3 O2 (g)
b. H2O (l) → H2O (s)
c. N2 (g) + 3 H2 (g) → 2 NH3 (g)
d. NaCl (s) → Na+ (aq) + Cl− (aq)
e. KCl (s) → KCl (l)
f.
CO2 (s) → CO2 (g)
g. 2 N2O5 (g) → 4 NO2 (g) + O2 (g)
2. Given a reaction where ∆H is negative and ∆S is positive, can you elucidate whether this reaction spontaneous? Are
there any conditions under which this equation is not spontaneous?
3. Given a reaction where ∆H is positive and ∆S is positive, can you elucidate whether this reaction spontaneous? Are
there any conditions under which this equation is not spontaneous?
4. What is the value of ∆G if ∆H = -32.0 kJ, ∆S = +25.0 J/mole∙K and T = 20 °C? Is this reaction spontaneous?
5.
For the reaction CO (g) + H2O (g) → CO2 (g) + H2 (g), given that ∆H = -41.2 kJ, ∆S = -135 J/mole∙K
and T = 25 °C what is the Gibbs Free Energy for this equation and is this reaction spontaneous?
6. Given the following information calculate the Gibbs free energy for the following reaction at 20 °C:
2 C3H7OH (l) + 9 O2 (g) → 6 CO2 (g) + 8 H2O (l)
Standard Heat of Formation
Absolute Entropy
∆Hf° in kJ mol-1
∆S° in J mol-1 K-1
C (s)
0.00
5.69
CO2 (g)
-393.5
213.6
H2 (g)
0.00
130.6
H2O (l)
-285.85
69.96
O2 (g)
0.00
205.0
C3H7OH (l)
-318.1
181.1
Substance
You are HIGHLY encouraged to watch the following videos on entropy! This is a new concept and can take a bit of time
to grasp, but if you put in the time, there are MANY things about the world around you which make so much more
sense! A full understanding of entropy is an amazing gift that you can give yourself! Feel free to ask questions!
https://youtu.be/lj5tqM5GZnQ
Perform an experiment from this video…Find the widest rubber band you can and cut it once (so you have a long strip of
rubber). Take the band, stretch it to its fullest extent quickly and immediately place it to your forehead or lips. What
is the temperature of the rubber band? Why???
Take the same strip and stretch it to its fullest extent and hold it until the temperature equilibrates with the room. Now,
allow the band to contract as quickly as you can (while still holding each end) and NOW place it to your forehead or
lips. What is the temperature of the rubber band now? Why???
Especially these two!!!!!
https://youtu.be/ROrovyJXSnM
https://youtu.be/iwarN7Kka5k
You will never find a better lecture on entropy than that by Richard Feynman.