Untitled Quiz

Podcast Beta

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What condition must be met for a system to be considered at equilibrium?

ΔS > 0

ΔG = 0 (correct)

ΔH < TΔS

ΔG < 0

What does the equation ΔG° = -RTlnKeq indicate?

The temperature dependence of ΔG at constant pressure.

The change in entropy at equilibrium.

The relationship between the change in free energy and equilibrium constant. (correct)

The relationship between ΔG° and the standard reaction quotient.

Which statement accurately describes the implications of ΔG° being greater than zero?

The reverse reaction is not favored.

The reaction will not occur spontaneously. (correct)

The reaction is at equilibrium.

The reaction is spontaneous in the forward direction.

Which of the following equations reflects the relationship necessary for a spontaneous process?

ΔG = ΔH - TΔS Signup and view all the answers

What is the condition for a process to be spontaneous according to Gibbs free energy?

ΔG < 0 Signup and view all the answers

What must the relationship between ΔG and Keq be at equilibrium?

ΔG° = 0 Signup and view all the answers

In a process controlled by enthalpy, what would be the characteristics of ΔH and ΔG?

ΔH large and negative; ΔG small and negative Signup and view all the answers

For a reaction where the change in Gibbs free energy is zero, which of the following statements is true?

The concentrations of reactants and products are constant. Signup and view all the answers

What happens to the Gibbs free energy (ΔG) at chemical equilibrium?

ΔG = 0 Signup and view all the answers

Given that ΔS represents entropy, which condition must be satisfied for a process to favor an increase in disorder?

ΔG < 0 Signup and view all the answers

What is the significance of a large positive ΔS in a process?

It can drive a spontaneous process despite unfavorable ΔH Signup and view all the answers

If isomerization of glucose-6-phosphate results in ΔG° of 2.1 kJ mol−1, what does this suggest about the reaction favorability under standard conditions?

The reaction does not favor product formation. Signup and view all the answers

For the reaction ATP → ADP + Pi with ΔG° = -30.5 kJ mol-1, what does this indicate about the reaction?

The reaction is spontaneous under standard conditions Signup and view all the answers

What is the significant condition for a spontaneous process at constant temperature and pressure?

ΔH - TΔS < 0 Signup and view all the answers

What does the term 'irreversible change' in a spontaneous process imply?

The reaction continues in one direction without reversing. Signup and view all the answers

In the unfolding of a protein with ΔH° = 250.8 kJ mol−1 and ΔS° = 752 J K−1 mol−1, above what temperature will the process be spontaneous?

Approximately 332.1 °C Signup and view all the answers

What is the standard state of free energies denoted by G°?

Value of G for a pure substance under specific conditions Signup and view all the answers

If ΔH is small and positive, and ΔS is significant and positive, what inference can be made about the overall process?

The process can still be spontaneous due to high entropy change Signup and view all the answers

How does temperature (T) influence the balance between ΔH and ΔS in determining ΔG?

Amplifies the effect of ΔS with increasing T Signup and view all the answers

Study Notes

Equilibrium

Equilibrium is defined by equilibrium constants (Keq)
Equilibrium constants predict the structure of systems
Systems are stable at equilibrium
Systems are unstable when not at equilibrium

Energy

Energy is defined by the first law ( enthalpy, H ) and second law (entropy, S) of thermodynamics
The change in Gibbs Free Energy (G) = H – TS
A system is at equilibrium when G = 0
A system undergoes spontaneous change when G < 0

Relationship between ΔG and Keq

At equilibrium, G° = −RTlnKeq
This relationship holds true at equilibrium
When not at equilibrium, use G − G° = RTlnKeq
G is the free energy of the system
G° is the free energy of the process at equilibrium

Tutorial: ΔG, Keq problem

The concentration of a solution of G3P was initially 0.05 M.
Isomerase was added.
After the mixture reached equilibrium at 25 °C, the concentration of G3P was 0.002 M.
ΔG° for the reaction can be calculated using the given data

Energy and Equilibrium of Systems

The first law of thermodynamics states that enthalpy (H) is equal to the heat (qp) transferred at constant pressure, or:
- H = qp= U + PV
Enthalpy concerns energy changes to the system during processes
Processes that lower enthalpy are favored
The second law of thermodynamics states that entropy (S) is equal to the heat (q) transferred divided by the temperature (T), or:
- S = q
Entropy concerns changes in the disorder of the system during processes
Processes that increase entropy are favored
We need a thermodynamic concept that captures both of these concepts

Criterion for the Direction of Spontaneous Change

For any spontaneous process at constant T and P:
- S > 𝑞𝑖𝑟𝑟𝑒𝑣  𝑇 or qirrev < TS
A spontaneous process implies irreversible change
q = H (const.T, P)
Therefore, H < TS or H − TS < 0
The process will continue as long as H − TS < 0

Gibbs Free Energy

We need a relationship such that H − TS < 0
Define Gibbs Free Energy as G = H − TS
The process will proceed as long as G < 0
G is known as the Gibbs free energy
G is a thermodynamic state function

ΔG = ΔH − TΔS

If G < 0, the process is favored in that direction
Equilibrium is reached when G = 0
If the H term dominates, have an enthalpy controlled process ( H large and –ve)
If the TS term dominates, have an entropy controlled process

Enthalpy vs. Entropy

The analysis of Mg2+ using complexation by EDTA is a good example
EDTA tetra sodium salt is widely used for the analysis of Mg ions in aqueous solution
Mg2+ ion is highly solvated by water
The method is used pharmaceutically, in pharmacology, biochemistry, etc.
Note, that the process goes essentially to completion i.e., fully to the right-hand side as drawn above

Enthalpy vs. Entropy

Can determine the relative contributions of enthalpy and entropy to the process.
We can determine the thermodynamic driving forces for the process and…
…infer the molecule-level processes
We find that H is small and +ve
But that S is significant and +ve
The release of five H2O molecules and two NaCl increases disorder, leading to more components generated
Overall G is –ve, making the process spontaneous from left to right as drawn

Standard States of Free Energies

G°: is the value of G for a pure substance under 1 atmosphere of pressure, at a specified temperature
G°: is the change in free energy when 1 mole of products in their standard states are converted to 1 mole of products in their standard states

Using ΔG Values, Example

ATP, ADP, and AMP are key molecules in biochemical energy transfer
We can use standard free energy values to calculate the change in free energy for a reaction

Tutorial: ΔG = ΔH − TΔS

1. ATP → ADP + Pi G° = −30.5 kJ mol−1
- (from thermal analysis, H° = −20.1 kJ mol−1)
- Calculate S° at 37 °C
- Comment on the significance of G, H and S values.
1. H° and S° for the unfolding of a protein are 250.8 kJ mol−1 and 752 J K−1 mol −1 respectively.
- Above what temperature (in °C) will unfolding of the protein be spontaneous?
- Comment on the values.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Untitled Quiz

Podcast Beta

Questions and Answers

What condition must be met for a system to be considered at equilibrium?

What does the equation ΔG° = -RTlnKeq indicate?

Which statement accurately describes the implications of ΔG° being greater than zero?

Which of the following equations reflects the relationship necessary for a spontaneous process?

What is the condition for a process to be spontaneous according to Gibbs free energy?

What must the relationship between ΔG and Keq be at equilibrium?

In a process controlled by enthalpy, what would be the characteristics of ΔH and ΔG?

For a reaction where the change in Gibbs free energy is zero, which of the following statements is true?

What happens to the Gibbs free energy (ΔG) at chemical equilibrium?

Given that ΔS represents entropy, which condition must be satisfied for a process to favor an increase in disorder?

What is the significance of a large positive ΔS in a process?

If isomerization of glucose-6-phosphate results in ΔG° of 2.1 kJ mol−1, what does this suggest about the reaction favorability under standard conditions?

For the reaction ATP → ADP + Pi with ΔG° = -30.5 kJ mol-1, what does this indicate about the reaction?

What is the significant condition for a spontaneous process at constant temperature and pressure?

What does the term 'irreversible change' in a spontaneous process imply?

In the unfolding of a protein with ΔH° = 250.8 kJ mol−1 and ΔS° = 752 J K−1 mol−1, above what temperature will the process be spontaneous?

What is the standard state of free energies denoted by G°?

If ΔH is small and positive, and ΔS is significant and positive, what inference can be made about the overall process?

How does temperature (T) influence the balance between ΔH and ΔS in determining ΔG?

Study Notes

Equilibrium

Energy

Relationship between ΔG and Keq

Tutorial: ΔG, Keq problem

Energy and Equilibrium of Systems

Criterion for the Direction of Spontaneous Change

Gibbs Free Energy

ΔG = ΔH − TΔS

Enthalpy vs. Entropy

Enthalpy vs. Entropy

Standard States of Free Energies

Using ΔG Values, Example

Tutorial: ΔG = ΔH − TΔS

Studying That Suits You

Related Documents

More Like This

Untitled Quiz

Untitled Quiz

Untitled Quiz

Untitled Quiz