Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are...
-
Upload
fiona-yeates -
Category
Documents
-
view
214 -
download
1
Transcript of Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are...
![Page 1: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/1.jpg)
Entropy and Free Energy
![Page 2: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/2.jpg)
Driving Forces of Reactions
• So far we have seen that reactions are spontaneous if they give off heat – exothermic
• There is a natural tendency in the universe for systems to get to lowest energy state
• Why do endothermic reactions happen?– Demo with barium – Ammonium chloride dissolving in H2O -
endothermic
![Page 3: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/3.jpg)
Natural direction
• Scientists notice that there is a natural direction for processes– Balls roll down hill, not up hill– Ice melts above 0º C, never refreezes above 0 C– A gas fills its container uniformly, never collects in one
area– Heat flows from hot to cold; hotter object doesn’t get
hotter when exposed to a colder object– Wood burns spontaneously, but CO2 and H2O don’t
form wood when heated
![Page 4: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/4.jpg)
What makes these processes irreversible?
• All of the processes have the following in common: – in all cases you have less information about how the
particles are organized than you did before
• Analogy: Why don’t we have fire drills during lunch?– Less “information” about where students are during
lunch compared to when they are in class
• Measure of “information” about a system = ENTROPY
![Page 5: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/5.jpg)
Entropy
• Measure of the amount of randomness or disorder in a system– Symbol: S– Units: J/K
• No matter what the process, entropy (of universe) is always increasing…
Entropy was introduced in 1865 by Rudolf J. E. Clausius, a German physicist. Clausius said he derived the term from the Greek words en trope, which means “in the transformation” He used it to describe the dissipation or apparent loss of energy available to do work as energy is transformed in a system.
![Page 6: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/6.jpg)
Entropy Analogies
• Throw a card into the air – 2 possible positions (up or down)
• Throw a deck of cards into the air – how many possible positions? – One possibility is that they land organized in a
stack. How probable is that? • The more cards = the more entropy• MORE MOLES = MORE ENTROPY
![Page 7: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/7.jpg)
Given the following reaction, how is entropy changing:
N2 (g) + 3 H2(g) 2NH3(g)
0% 0%0%
100%1. Increasing
2. Decreasing
3. Stays the same
4. Need more information
![Page 8: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/8.jpg)
What causes entropy to increase?• Statistics…• Boltzmann Bucks Demo
– At first everyone has $1, we play rock-paper-scissors for awhile. Some people have more money than others, but • no one has all the money and • Not everyone has exactly $1
– Why not? A. There is only one way for the money to be arranged so that
everyone has $1B. There are only 9 ways for the money to be arranged so that one
person has $9 (assuming class size of 9)C. There are many ways for some people to have no money, some to
have $1 and some to have $2 or $3.D. So there is a higher probability that the $ will be arranged as
described in C• Nature spontaneously proceeds to the state that has the
highest probability of existing.• Highest probability = most disordered
![Page 9: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/9.jpg)
Entropy Changes
• Increase moles• Dissolving and mixing• Increasing temperature• Increase volume• Solid to liquid or liquid to gas (or S to G)• More complicated molecules have higher
S than simpler molecles
![Page 10: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/10.jpg)
Which one of the following does not generally lead to an increase in
entropy of a system?
0%
100%
0%0%
1. Increase in total number of moles or particles
2. Formation of a solution
3. Formation of a gas
4. Formation of a solid
![Page 11: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/11.jpg)
Given the reaction below, how is entropy changing?
Br2(l) Br2(g)100%
0%0%0%
1. Increasing
2. Decreasing
3. Stays the same
4. Need more info
![Page 12: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/12.jpg)
Given the following reaction, how is entropy changing:
Ag+1(aq) + Cl-1(aq) AgCl(s)
10%0%0%
90%1. Increasing
2. Decreasing
3. Stays the same
4. Need more info
![Page 13: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/13.jpg)
Given the following reaction, how is entropy changing: 2NO2(g) N2O4(g)
10%0%0%
90%1. Increasing
2. Decreasing
3. Stays the same
4. Need more info
![Page 14: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/14.jpg)
Given the following reaction, how is entropy changing:
CO(g) + H2O(g) CO2(g) + H2(g)
0% 0%0%
100%1. Increasing
2. Decreasing
3. Stays the same
4. Need more info
![Page 15: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/15.jpg)
Given the following reaction, how is entropy changing:
H2(g) + F2(g) 2HF(g)
0% 0%0%0%
1. Increasing
2. Decreasing
3. Stays the same
4. Need more info
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
![Page 16: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/16.jpg)
Given the following reaction, what is the sign for ΔS:
NaCl(s) NaCl(aq)
0% 0%0%0%
1. positive
2. negative
3. 0
4. Need more info
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
![Page 17: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/17.jpg)
Given the following reaction, how is entropy changing:
2OH-(aq) + CO2(g) H2O(l) + CO32- (aq)
0% 0%0%0%
1. Increasing
2. Decreasing
3. Stays the same
4. Need more info
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
![Page 18: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/18.jpg)
Which of the following has the largest increase in entropy?
0% 0%0%0%
1. Pb(NO3)2(s) Pb(NO3)2(aq)
2. CaCO3(s) CaO(s) + CO2(g)
3. 2NH3 (g) 2H2(g) + N2(g)
4. H2(g) + Br2(g) 2HBr(g)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
![Page 19: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/19.jpg)
Spontaneity
• Spontaneous change:– Occurs w/o continuous input of energy
• Spontaneous reactions occur when– Reaction is exothermic ( ΔH < 0)– Increase in entropy for the system (ΔS >0)
• But which is more important? ΔH or ΔS ?
![Page 20: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/20.jpg)
Total Entropy
• System vs. Surroundings vs. Universe– Suniverse = Ssystem + Ssurroundings
– Suniv is always increasing.• Two spontaneous processes:
– CaCl2(s) Ca2+(aq) + Cl-1(aq) ΔH = -66kJ • Ssys is increasing• Ssurr is increasing because heat is released to surroundings
– NH4Cl(s) NH4+ + Cl-(aq) ΔH = 15 kJ
• Ssys is increasing• Ssurr is decreasing b/c surroundings are losing heat
• Non-spotaneous– Na(s) Na (l) ΔH =2.59 kJ
• Ssys = increasing• Ssurr = decreasing
![Page 21: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/21.jpg)
A. NH4Cl(s) NH4+ + Cl-(aq) ΔH = 15 kJ
B. Na(s) Na (l) ΔH =2.59 kJ
C. Na+(g) + Cl-(g) NaCl(s) ΔH = -771 kJ
• Why is A spontaneous, but not B?– Entropy is much greater for A
• Why is C spontaneous?– Enthalpy is large
![Page 22: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/22.jpg)
How do you know if enthalpy or entropy will make the reaction more
spontaneous?
• Remember: Suniverse = Ssystem + Ssurroundings
• Ssurr depends on temperature• The lower the surrounding temperature, the more significant
adding heat is• The higher the surrounding temp, the less significant adding
heat is.
– Analogy• Imagine you give $1 to someone w/ only $10 to their name? • Imagine the effect of giving $1 to a millionaire.• Who is affected more? sys
surr
HS
T
![Page 23: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/23.jpg)
• Exothermic reactions that release heat to the surroundings are a a stronger driver of reactions when the surrounding temperature is low.
• At high temperatures, an exothermic reaction isn’t such a strong driving force, entropy is more important.
Negative sign b/c ΔH defined in terms of system: exothermic reaction from system’s perspective causes increase in entropy of surroundings. • Suniverse = Ssystem + Ssurroundings
Entropy of system
Determined by ΔH of system
syssurr
HS
T
![Page 24: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/24.jpg)
• Suniv = Ssys + Ssurr
• Substitute: - ΔHsys/T for Ssurr
• Multiply by (-T)• Define new quantity
– Free energy: ΔG = -T ΔSuniv
– Free energy tells whether a rxn will be spontaneous at a given temperature.
– Measures the maximum energy available to do useful work
– Reactions at equilibrium have ΔG = 0
syssurr
HS
T
-T ΔSuniv = ΔHsys - T ΔSsys
ΔG = ΔHsys - T ΔSsys
![Page 25: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/25.jpg)
Based on the previous slides and derivation of ΔG, rxns will be
spontaneous if ΔG is
75%
0%
13%13%
1. Less than 0
2. Greater than 0
3. Equal to 0
4. Spontaneity has nothing to do with ΔG.
![Page 26: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/26.jpg)
Under which conditions will reactions ALWAYS be spontaneous?
0%
11%
78%
11%
1. ΔH > 0, ΔS >0
2. ΔH > 0, ΔS < 0
3. ΔH < 0, ΔS >0
4. ΔH < 0, ΔS <0
ΔG = ΔHsys - T ΔSsys
![Page 27: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/27.jpg)
Under which conditions will reactions NEVER be spontaneous?
0% 0%0%
100%
1. ΔH > 0, ΔS >0
2. ΔH > 0, ΔS < 0
3. ΔH < 0, ΔS >0
4. ΔH < 0, ΔS <0
ΔG = ΔHsys - T ΔSsys
![Page 28: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/28.jpg)
Under which conditions will reactions be spontaneous at high temps?
(other than when they are always spontaneous)
100%
0%0%0%
1. ΔH > 0, ΔS >0
2. ΔH > 0, ΔS < 0
3. ΔH < 0, ΔS >0
4. ΔH < 0, ΔS <0
ΔG = ΔHsys - T ΔSsys
![Page 29: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/29.jpg)
ΔH > 0, ΔS >0
• A large positive value for the term (TΔS) can make ΔG negative if it is bigger than ΔH
• Reaction is endothermic so the entropy of surroundings is decreasing. At high temps, this won’t make as big of a difference as it would at lower temps.
ΔG = ΔHsys - T ΔSsys
syssurr
HS
T
![Page 30: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/30.jpg)
Under which conditions will reactions be spontaneous at low temps?
(other than when they are always spontaneous)
0%
80%
10%10%
1. ΔH > 0, ΔS >0
2. ΔH > 0, ΔS < 0
3. ΔH < 0, ΔS >0
4. ΔH < 0, ΔS <0
ΔG = ΔHsys - T ΔSsys
![Page 31: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/31.jpg)
ΔH < 0, ΔS < 0
• A small negative value for the term (TΔS) can still make ΔG negative if it is smaller than the absolute value of ΔH
• Reaction is exothermic so the entropy of surroundings is increasing. At low temps, this will make a bigger difference than it would at higher temps.
ΔG = ΔHsys - T ΔSsys
syssurr
HS
T
![Page 32: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/32.jpg)
Calculating ΔG
• For a reaction at 25 C, ΔH = 100 kJ and ΔS = 80 J/K, determine if the reaction is spontaneous.
• For a reaction with a ΔH = 100 kJ and a ΔS of 80 J/K, at what temperature will the reaction become spontaneous?
Watch your units!! Put temps in Kelvin and make sure you aren’t trying to add Joules to Kilojoules!
![Page 33: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/33.jpg)
• 100 KJ – (298*80/1000) = 76.2 kJ = not spontaneous
• 0 = 100 - (x*80/1000) 100 = x(. 08)• x = 1250 K, reaction becomes
spontaneous at temperatures above 1250 K
![Page 34: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/34.jpg)
Calculations of ΔS°rxn, ΔH°rxn and ΔG°rxn
• Standard Entropy of Formation Tables (ΔS°f )– Σ n(ΔS°f )products - Σ n(ΔS°f )reactants
• Standard Gibbs Free Energy of Formation Tables (ΔG°f )– Σ n(ΔG°f )products - Σ n(ΔG°f )reactants
• Standard Gibbs Free Energy of Formation Tables (ΔG°f )– Σ n(ΔG°f )products - Σ n(ΔG°f )reactants
– Only good for standard conditions! – For ΔG at non-standard conditions, use
ΔG = ΔH - TΔS
![Page 35: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/35.jpg)
• Calculate the free-energy change, DG°, for the oxidation of ethyl alcohol to acetic acid using standard free energies of formation.
CH3CH2OH(l) + O2(g) CH3COOH(l) + H2O(l)
![Page 36: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/36.jpg)
CH3CH2OH(l) + O2(g) CH3COOH(l) + H2O(l)
DGf°, kJ/mol –174.8 0 –392.5 –237.2
n, mol 1 1 1 1
nDGf°, kJ –174.8 0 –392.5 –237.2 –174.8 kJ –629.7 kJ
DG° = –454.9 kJ
DG° = –629.7 – (–174.8)
![Page 37: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/37.jpg)
• Sodium carbonate, Na2CO3, can be prepared by heating sodium hydrogen carbonate, NaHCO3:
2NaHCO3(s) Na2CO3(s) + H2O(g) + CO2(g)
Estimate the temperature at which the reaction proceeds spontaneously at 1 atm.
See Appendix C for data.
![Page 38: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/38.jpg)
2NaHCO3(s) Na2CO3(s) + H2O(g) + CO(g)DHf°, kJ/mol –947.7 –1130.8 –241.8 –393.5n, mol 2 1 1 1nDHf°, kJ –1895.4 –1130.8 –241.8 –393.5
–1895.4 kJ –1766.1 kJDH° = 129.3 kJ
Sf°, J/mol K 102 139 188.7 213.7n, mol 2 1 1 1nSf°, J/K 204 139 188.7 213.7
204 J/K 541.4 J/KDS° = 337.4 J/K
![Page 39: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/39.jpg)
S
HT
Δ
Δ
KJ
337.4
J 10 129.3 3T
K 383T
C110T
![Page 40: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/40.jpg)
Use ΔG to get K
• Equilibrium position represents the lowest free energy value available to a particular reaction system
![Page 41: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/41.jpg)
ΔG and K• Standard free energy change is related to the
thermodynamic equilibrium constant, K, at equilibrium.– IF a reaction is NOT at equilibrium, it is proceeding in some
direction (forward or reverse) depending on Q, reaction quotient. – That means there exists energy to do work (make reaction
proceed)• ΔG = Δ G° + RT ln Q
• At equilibrium:– Δ G = 0, because there is no ability to do any more useful work – and Q = K
• So we get: – Δ G° = –RT ln K
![Page 42: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/42.jpg)
• Calculate the value of the thermodynamic equilibrium constant at 25°C for the reaction
• N2O4(g) 2NO2(g)
• The standard free energy of formation at 25°C is 51.30 kJ/mol for NO2 and 97.82 kJ/mol for N2O4(g).
![Page 43: Entropy and Free Energy. Driving Forces of Reactions So far we have seen that reactions are spontaneous if they give off heat – exothermic There is a.](https://reader036.fdocuments.us/reader036/viewer/2022070308/551ba512550346167e8b5c56/html5/thumbnails/43.jpg)
RT
GK
ln
K) (298K mol
J 8.315
)mol
J 10 (4.78
ln
3K
929.1 ln K
0.145K
DG° = 2 mol(51.30 kJ/mol) – 1 mol(97.82 kJ/mol)
DG° = 102.60 kJ – 97.82 kJ
DG° = 4.78 kJ