Ch. 6 - Thermodynamics and KineticsWorksheetSee all chapters
All Chapters
Ch. 1 - A Review of General Chemistry
Ch. 2 - Molecular Representations
Ch. 3 - Acids and Bases
Ch. 4 - Alkanes and Cycloalkanes
Ch. 5 - Chirality
Ch. 6 - Thermodynamics and Kinetics
Ch. 7 - Substitution Reactions
Ch. 8 - Elimination Reactions
Ch. 9 - Alkenes and Alkynes
Ch. 10 - Addition Reactions
Ch. 11 - Radical Reactions
Ch. 12 - Alcohols, Ethers, Epoxides and Thiols
Ch. 13 - Alcohols and Carbonyl Compounds
Ch. 14 - Synthetic Techniques
Ch. 15 - Analytical Techniques: IR, NMR, Mass Spect
Ch. 16 - Conjugated Systems
Ch. 17 - Aromaticity
Ch. 18 - Reactions of Aromatics: EAS and Beyond
Ch. 19 - Aldehydes and Ketones: Nucleophilic Addition
Ch. 20 - Carboxylic Acid Derivatives: NAS
Ch. 21 - Enolate Chemistry: Reactions at the Alpha-Carbon
Ch. 22 - Condensation Chemistry
Ch. 23 - Amines
Ch. 24 - Carbohydrates
Ch. 25 - Phenols
Ch. 26 - Amino Acids, Peptides, and Proteins

Time for Gibbs Free Energy, the most important equation for understanding reaction favorability! It’s going to be important that we understand the significance of all the terms in this equation.  

Concept #1: Breaking down the different terms of the Gibbs Free Energy equation. 

1. Enthalpy (ΔH°) is the sum of bond dissociation energies for the reaction.

  • Negative values (-) indicate the making of new bonds = Exothermic
  • Positive values (+) indicate the breaking of new bonds = Endothermic

 

2. Entropy (ΔS) is the tendency of a system to take its most probable form.

  • Negative values (-) indicate less probable = Unfavored
  • Positive values (+) indicate more probable = Favored

 

3. Temperature (T) amplifies the effect of entropy on the overall favorability.

Concept #2: Intermediates vs. Transition States 

  • Some reactions require more than one step to go to completion. The ΔGo is the sum of all the steps

 

  • Transition states are high-energy species that CANNOT be isolated. They involve bonds being broken and made at the same time.

 

  • Intermediates are high-energy species that CAN be isolated. They rest at a higher energy state than normal.
Additional Problems
Consider the following reaction: Is the sign of ΔG dependent on temperature?
Consider the following reaction: Is the magnitude of ΔG dependent on temperature?
Which value of ΔG corresponds with K eq = 1? (a) +1 kJ/mol (b) 0 kJ/mol (c) -1 kJ/mol
Predict the sign of ΔG for an exothermic reaction with an increase in entropy. a) cannot predict b) positive c) negative d) no change e) Aquarius
Predict the sign of ΔG for an endothermic reaction with a decrease in entropy. a) cannot predict b) positive c) negative d) no change e) Aquarius
In an acid base reaction where the products predominates, ΔG° < 0 ( True or False )
For the following reaction, indicate by circling the correct answers for  ΔG and K, whether this reaction lies to the right or left.
The iodination of ethylene at 25°C is characterized by the thermodynamic values shown. H2C = CH2(g) + I2(g) ⇌ lCH2CH2l(g)     ΔH° = - 48 kJ; ΔS° = - 0.13 kJ/K (b) Is the reaction exergonic or endergonic at 25°C?
Consider the following reaction: (e) Is ΔG for this process positive or negative?  
Consider the following reaction: (f) Would you expect an increase in temperature to have a significant impact on the position of equilibrium (equilibrium concentrations)? Explain.  
Consider the following reaction: (j) How will the rate be affected if the concentration of hydroxide is doubled?  
The reaction of chloroethane with water in the gas phase to produce ethanol and hydrogen chloride has ΔH° = +26.6 kJ mol -1 and ΔS° = +4.81 J K-1 mol-1 at 25°C. (b) Calculate ΔG° for the reaction. What can you now say about whether the reaction will proceed to completion?    
Draw the following energy diagram with the following requirements:A reaction that has 3 steps and overall is endergonic. Step 1 is endergonic, Steps 2 and 3 are both exergonic. Step 1 is the rate determining step.  
For the following, circle the capitalized word that best completes the statement.In general, it is best to think of alkenes and alkynes as NUCLEOPHILES or ELECTROPHILES that react with NUCLEOPHILES or ELECTROPHILES.In general, NUCLEOPHILES or ELECTROPHILES serve as electron sources and NUCLEOPHILES or ELECTROPHILES serve as electron sinks for most reactions.A pi bond or lone pair will serve as an ELECTRON SOURCE or ELECTRON SINK for an arrow that indicates the making of a new bond.An atom that can accommodate a new bond can serve as an ELECTRON SOURCE or ELECTRON SINK for an arrow that indicates the making of a new bond.A reaction that occurs faster (greater opportunity) has a LOWER or HIGHER activation energy.A reation that has a strong thermodynamic driving force (a strong motive) is FAVORABLE or UNFAVORABLE as written.
Classify states 2–4 in the potential energy diagram.A. 2, 3, and 4 are transition statesB. 2, 3, and 4 are reactive intermediatesC. 2 and 4 are transition states; 3 is a reactive intermediateD. 2 and 4 are reactive intermediates; 3 is a transition state 
Which of the following has ΔG°f = 0 at 25°C?a. O3(g)b. O(g)c. H2O(g)d. H2O(l)e. Na(s)