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Questions and Answers
What is the change in free energy (ΔG) for the reaction 2 A(g) + B2(g) → 2 AB(g)?
What is the change in free energy (ΔG) for the reaction 2 A(g) + B2(g) → 2 AB(g)?
- −400 kJ
- −100 kJ
- −200 kJ (correct)
- −250 kJ
Which expression correctly determines the temperature at which a reaction becomes spontaneous?
Which expression correctly determines the temperature at which a reaction becomes spontaneous?
- T = ΔH / ΔS (correct)
- T = ΔH / ΔG
- T = ΔS / ΔG
- T = ΔG / ΔS
At which temperature is the standard free energy change measured?
At which temperature is the standard free energy change measured?
- 310 K
- 298 K (correct)
- 350 K
- 250 K
What happens to the value of ΔG as the temperature increases for a spontaneous reaction?
What happens to the value of ΔG as the temperature increases for a spontaneous reaction?
What is the standard Gibbs free energy of formation (ΔG°f) for B2(g)?
What is the standard Gibbs free energy of formation (ΔG°f) for B2(g)?
What is a primary factor that leads to an increase in entropy within a system?
What is a primary factor that leads to an increase in entropy within a system?
In which of the following processes is the entropy change (ΔS) expected to be negative?
In which of the following processes is the entropy change (ΔS) expected to be negative?
What is meant by microstates in relation to entropy?
What is meant by microstates in relation to entropy?
What happens to entropy (S) when the temperature of a system increases?
What happens to entropy (S) when the temperature of a system increases?
For the reaction 2 KClO3(s) → 2 KCl(s) + 3 O2(g), what is the expected sign of ΔS and why?
For the reaction 2 KClO3(s) → 2 KCl(s) + 3 O2(g), what is the expected sign of ΔS and why?
According to Boltzmann's equation, which variable represents the number of energetically equivalent arrangements?
According to Boltzmann's equation, which variable represents the number of energetically equivalent arrangements?
Which statement is true regarding the physical states of matter and their entropic behavior?
Which statement is true regarding the physical states of matter and their entropic behavior?
In the context of chemical thermodynamics, what does an increase in the number of gas particles do to system entropy?
In the context of chemical thermodynamics, what does an increase in the number of gas particles do to system entropy?
What is the value of W when there are two particles and four possible locations?
What is the value of W when there are two particles and four possible locations?
What happens to the number of microstates when the divider is removed from a box containing two particles?
What happens to the number of microstates when the divider is removed from a box containing two particles?
Which of the following statements about macrostates is true?
Which of the following statements about macrostates is true?
How many possible arrangements (microstates) exist when particles A and B are together in a single location?
How many possible arrangements (microstates) exist when particles A and B are together in a single location?
For two particles A and B in separate locations, how many microstates can be formed?
For two particles A and B in separate locations, how many microstates can be formed?
Which configuration of particles A and B corresponds to the least probable macrostate?
Which configuration of particles A and B corresponds to the least probable macrostate?
What does removing the divider imply for the relationship between microstates and macrostates?
What does removing the divider imply for the relationship between microstates and macrostates?
Which statement best explains the relationship between microstates and macrostates?
Which statement best explains the relationship between microstates and macrostates?
What is the value of ΔS° for the vaporization of liquid mercury?
What is the value of ΔS° for the vaporization of liquid mercury?
At what minimum temperature does the vaporization of mercury become spontaneous?
At what minimum temperature does the vaporization of mercury become spontaneous?
What is the standard free energy change for the formation of water from hydrogen and oxygen according to the reaction provided?
What is the standard free energy change for the formation of water from hydrogen and oxygen according to the reaction provided?
In the equation for calculating the standard Gibbs free energy change, which variable represents the temperature in Kelvin?
In the equation for calculating the standard Gibbs free energy change, which variable represents the temperature in Kelvin?
Which formula calculates the change in free energy for a reaction under nonstandard conditions?
Which formula calculates the change in free energy for a reaction under nonstandard conditions?
What is the significance of the variable R in the equation ΔG = ΔG° + RT ln Q?
What is the significance of the variable R in the equation ΔG = ΔG° + RT ln Q?
Which reaction has a standard free energy change (ΔG°) of -2108.2 kJ as shown in the example?
Which reaction has a standard free energy change (ΔG°) of -2108.2 kJ as shown in the example?
How is the value of ΔH° for the vaporization of mercury determined?
How is the value of ΔH° for the vaporization of mercury determined?
What is ΔGrxn° for the reaction: 2 A(g) + B2(g) → 2 AB(g) given the choices?
What is ΔGrxn° for the reaction: 2 A(g) + B2(g) → 2 AB(g) given the choices?
Which equation is used to find the standard free energy change of a reaction?
Which equation is used to find the standard free energy change of a reaction?
What is the correct value of the standard free energy of formation for oxygen gas (O2)?
What is the correct value of the standard free energy of formation for oxygen gas (O2)?
What do the ΔGf° values represent in thermodynamics?
What do the ΔGf° values represent in thermodynamics?
In the equation ΔG° = ΔH° - TΔS°, which factor influences Gibbs free energy by accounting for disorder?
In the equation ΔG° = ΔH° - TΔS°, which factor influences Gibbs free energy by accounting for disorder?
What is the value of ΔG when calculated using the equation ΔG = ΔG° + RT ln Q?
What is the value of ΔG when calculated using the equation ΔG = ΔG° + RT ln Q?
What does a negative ΔG value indicate about the reaction's spontaneity?
What does a negative ΔG value indicate about the reaction's spontaneity?
Calculate the exponent in the equation for equilibrium constant K when ΔG° is -32.8 kJ.
Calculate the exponent in the equation for equilibrium constant K when ΔG° is -32.8 kJ.
What is the expression for the equilibrium constant (K) at 298 K based on ΔG°?
What is the expression for the equilibrium constant (K) at 298 K based on ΔG°?
Given the calculated ΔG° for the Haber process, what is the equilibrium constant K?
Given the calculated ΔG° for the Haber process, what is the equilibrium constant K?
Which components are necessary to calculate Qp for a reaction involving pressures?
Which components are necessary to calculate Qp for a reaction involving pressures?
What does the term Q represent in the reaction's context?
What does the term Q represent in the reaction's context?
At which temperature was ΔG calculated in the given example?
At which temperature was ΔG calculated in the given example?
Flashcards
Entropy (S)
Entropy (S)
A measure of disorder or randomness in a system.
ΔS > 0
ΔS > 0
Entropy increases in a chemical process.
ΔS < 0
ΔS < 0
Entropy decreases in a chemical process.
Solid to liquid phase change
Solid to liquid phase change
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Liquid to gas phase change
Liquid to gas phase change
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Increase in temperature
Increase in temperature
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Microstates
Microstates
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Boltzmann constant (k)
Boltzmann constant (k)
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Calculating W
Calculating W
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Most Probable Macrostate
Most Probable Macrostate
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Two particles, four locations
Two particles, four locations
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16 microstates (2 particles, 4 locations)
16 microstates (2 particles, 4 locations)
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Macrostates Example
Macrostates Example
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Standard Gibbs Free Energy of Formation (ΔG°f)
Standard Gibbs Free Energy of Formation (ΔG°f)
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Gibbs Free Energy Change (ΔG°rxn)
Gibbs Free Energy Change (ΔG°rxn)
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Calculating ΔG°rxn
Calculating ΔG°rxn
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Spontaneous Reaction
Spontaneous Reaction
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Gibbs Free Energy at Non-Standard Temperatures
Gibbs Free Energy at Non-Standard Temperatures
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Gibbs Free Energy Change
Gibbs Free Energy Change
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Non-Standard Conditions
Non-Standard Conditions
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Reaction Quotient (Q)
Reaction Quotient (Q)
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Equation for Non-standard Gibbs Free Energy Change
Equation for Non-standard Gibbs Free Energy Change
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Gibbs Free Energy (G)
Gibbs Free Energy (G)
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Standard Free Energy of Formation (DG°f)
Standard Free Energy of Formation (DG°f)
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Standard Free Energy Change (DG°rxn)
Standard Free Energy Change (DG°rxn)
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How to calculate DG°rxn
How to calculate DG°rxn
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Non-Spontaneous Reaction
Non-Spontaneous Reaction
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What does DG°rxn tell us about a reaction?
What does DG°rxn tell us about a reaction?
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Example: Combustion of propane (C3H8)
Example: Combustion of propane (C3H8)
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Standard Gibbs Free Energy Change (ΔG°)
Standard Gibbs Free Energy Change (ΔG°)
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Equilibrium Constant (K)
Equilibrium Constant (K)
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Relationship between ΔG and K
Relationship between ΔG and K
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Equilibrium
Equilibrium
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Study Notes
Chemical Thermodynamics
- The study of energy changes in chemical and physical processes
- Entropy (S) measures disorder or randomness in a system
- Entropy increases when there's a phase change from condensed to less condensed (solid → liquid → gas)
- Entropy increases with more temperature or higher kinetic energy in a given phase
- Entropy increases with more particles or dissolution in an aqueous solution, allowing for more energy distribution.
- Entropy changes (ΔS) are positive for processes that increase disorder and negative for processes that decrease disorder.
- The third law of thermodynamics states that the entropy of a perfectly ordered, crystalline substance at absolute zero is zero (Scrystal (0 K) = 0)
- Boltzmann's equation defines entropy mathematically: S = k ln W
- Microstates are energetically equivalent arrangements (microstates) possible for a system.
- The more microstates, the higher the entropy.
- The most probable macrostate is the one with the highest number of microstates.
- A system will spontaneously move to a more disordered arrangement
- The spontaneity of a process depends on both the system and surroundings
- The Second Law of Thermodynamics: Spontaneous processes always cause an overall increase in entropy (S) of the universe
- Standard Molar Entropies (S°) are calculated by the third law of thermodynamics.
- Standard changes in entropy (∆Sorxn) are calculated by using the standard molar entropies of the reactants and products. ∆S°rxn = Σm[S°(products)]-Σn[S°(reactants)]
- Gibbs Free Energy (G) is a state function for predicting process spontaneity at a given temperature. (G = H – TS)
- The change in Gibbs free energy under standard conditions: ΔG° = ΔH° – TΔS°
- ΔG° > 0: reaction is non-spontaneous forward.
- ΔG° < 0: reaction is spontaneous forward.
- ΔG° = 0: reaction is at equilibrium.
- Standard free energy of formation (ΔG°f) is the change in free energy when one mole of a compound is formed from its elements in their standard states
- ΔGrxn=Σm[ΔGf(products)] -Σn[ΔGf(reactants)]
- Temperature dependence of free energy change: ∆G = ∆G° + RT ln Q where Q is the reaction quotient and R is the gas constant.
- The standard change in free energy can be used to calculate the equilibrium constant. ∆G° = −RT ln K, where K is the equilibrium constant.
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