Gibbs Free Energy and Thermodynamic Favorability - AP Chemistry
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Which variable in $\Delta G = \Delta H - T\Delta S$ is affected by temperature changes?
Which variable in $\Delta G = \Delta H - T\Delta S$ is affected by temperature changes?
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The $T\Delta S$ term. Only the entropy term $T\Delta S$ contains temperature as a variable.
The $T\Delta S$ term. Only the entropy term $T\Delta S$ contains temperature as a variable.
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State the relationship between $K_{eq}$ and $\Delta G^\circ$.
State the relationship between $K_{eq}$ and $\Delta G^\circ$.
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$\Delta G^\circ = -RT \ln K_{eq}$. This equation connects equilibrium constants to standard free energy changes.
$\Delta G^\circ = -RT \ln K_{eq}$. This equation connects equilibrium constants to standard free energy changes.
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Explain the effect of $\Delta S > 0$ on a reaction's spontaneity.
Explain the effect of $\Delta S > 0$ on a reaction's spontaneity.
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It favors spontaneity. Positive entropy change makes the $-T\Delta S$ term negative, favoring spontaneity.
It favors spontaneity. Positive entropy change makes the $-T\Delta S$ term negative, favoring spontaneity.
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What is the standard state temperature for $\Delta G^\circ$ calculations?
What is the standard state temperature for $\Delta G^\circ$ calculations?
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$298 \text{ K}$. Standard temperature for thermodynamic calculations is 25°C or 298 K.
$298 \text{ K}$. Standard temperature for thermodynamic calculations is 25°C or 298 K.
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What does a positive $\Delta G^\circ$ indicate about a reaction?
What does a positive $\Delta G^\circ$ indicate about a reaction?
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The reaction is non-spontaneous. Positive standard free energy means unfavorable under standard conditions.
The reaction is non-spontaneous. Positive standard free energy means unfavorable under standard conditions.
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How is $\Delta G$ calculated for a reaction not at equilibrium?
How is $\Delta G$ calculated for a reaction not at equilibrium?
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$\Delta G = \Delta G^\circ + RT \ln Q$. This equation accounts for non-standard conditions using the reaction quotient.
$\Delta G = \Delta G^\circ + RT \ln Q$. This equation accounts for non-standard conditions using the reaction quotient.
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In terms of enthalpy and entropy, when is a process always spontaneous?
In terms of enthalpy and entropy, when is a process always spontaneous?
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$\Delta H < 0$ and $\Delta S > 0$. Exothermic with positive entropy ensures $\Delta G$ is always negative.
$\Delta H < 0$ and $\Delta S > 0$. Exothermic with positive entropy ensures $\Delta G$ is always negative.
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Identify the units of Gibbs free energy change, $\Delta G$.
Identify the units of Gibbs free energy change, $\Delta G$.
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Joules (J) or kilojoules (kJ). Energy units since $\Delta G$ represents energy change per mole of reaction.
Joules (J) or kilojoules (kJ). Energy units since $\Delta G$ represents energy change per mole of reaction.
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Is a reaction with $K_{eq} > 1$ product-favored or reactant-favored?
Is a reaction with $K_{eq} > 1$ product-favored or reactant-favored?
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Product-favored. Large equilibrium constants indicate reactions favor product formation.
Product-favored. Large equilibrium constants indicate reactions favor product formation.
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When is a process never spontaneous at any temperature?
When is a process never spontaneous at any temperature?
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$\Delta H > 0$ and $\Delta S < 0$. Endothermic with negative entropy makes $\Delta G$ always positive.
$\Delta H > 0$ and $\Delta S < 0$. Endothermic with negative entropy makes $\Delta G$ always positive.
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What is the significance of $T\Delta S$ in the Gibbs free energy equation?
What is the significance of $T\Delta S$ in the Gibbs free energy equation?
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It represents the temperature-dependent entropy term. This term quantifies the entropy contribution weighted by temperature.
It represents the temperature-dependent entropy term. This term quantifies the entropy contribution weighted by temperature.
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Identify the role of catalysts in altering $\Delta G$.
Identify the role of catalysts in altering $\Delta G$.
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Catalysts do not alter $\Delta G$. Catalysts only affect reaction rates, not thermodynamic quantities.
Catalysts do not alter $\Delta G$. Catalysts only affect reaction rates, not thermodynamic quantities.
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What is the value of $R$ in the equation $\Delta G^\circ = -RT \ln K_{eq}$?
What is the value of $R$ in the equation $\Delta G^\circ = -RT \ln K_{eq}$?
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8.314 J/(mol·K). The universal gas constant in SI units for thermodynamic calculations.
8.314 J/(mol·K). The universal gas constant in SI units for thermodynamic calculations.
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Which term in the Gibbs free energy equation accounts for disorder?
Which term in the Gibbs free energy equation accounts for disorder?
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$\Delta S$. Entropy measures the randomness or disorder of the system.
$\Delta S$. Entropy measures the randomness or disorder of the system.
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What is the thermodynamic favorability of a reaction with $\Delta G^\circ = -40 \text{ kJ/mol}$?
What is the thermodynamic favorability of a reaction with $\Delta G^\circ = -40 \text{ kJ/mol}$?
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Favorable. Large negative $\Delta G^\circ$ values indicate highly favorable reactions.
Favorable. Large negative $\Delta G^\circ$ values indicate highly favorable reactions.
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What condition must be met for a process to be spontaneous?
What condition must be met for a process to be spontaneous?
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$\Delta G < 0$. Spontaneous processes have negative free energy changes.
$\Delta G < 0$. Spontaneous processes have negative free energy changes.
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What does $\Delta G = 0$ signify for a system at equilibrium?
What does $\Delta G = 0$ signify for a system at equilibrium?
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The system is at equilibrium. Zero $\Delta G$ indicates no net driving force for change in either direction.
The system is at equilibrium. Zero $\Delta G$ indicates no net driving force for change in either direction.
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How does $\Delta G$ relate to the maximum useful work a system can perform?
How does $\Delta G$ relate to the maximum useful work a system can perform?
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$\Delta G$ equals the maximum useful work. The magnitude of $\Delta G$ represents maximum work extractable from the process.
$\Delta G$ equals the maximum useful work. The magnitude of $\Delta G$ represents maximum work extractable from the process.
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What is the expression for $\Delta S_{univ}$ in terms of $\Delta G$?
What is the expression for $\Delta S_{univ}$ in terms of $\Delta G$?
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$\Delta S_{univ} = -\frac{\Delta G}{T}$. This relates universal entropy change to Gibbs free energy change.
$\Delta S_{univ} = -\frac{\Delta G}{T}$. This relates universal entropy change to Gibbs free energy change.
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Given $\Delta G = -10 \text{ kJ/mol}$, is the reaction spontaneous?
Given $\Delta G = -10 \text{ kJ/mol}$, is the reaction spontaneous?
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Yes, it is spontaneous. Negative $\Delta G$ values always indicate spontaneous processes.
Yes, it is spontaneous. Negative $\Delta G$ values always indicate spontaneous processes.
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For which $\Delta H$ and $\Delta S$ values is spontaneity temperature-dependent?
For which $\Delta H$ and $\Delta S$ values is spontaneity temperature-dependent?
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$\Delta H$ and $\Delta S$ both positive or both negative. Temperature determines which term dominates in the Gibbs equation.
$\Delta H$ and $\Delta S$ both positive or both negative. Temperature determines which term dominates in the Gibbs equation.
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What does $\Delta G > 0$ indicate about a system's state?
What does $\Delta G > 0$ indicate about a system's state?
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It is non-spontaneous. Positive $\Delta G$ means the process requires energy input to proceed.
It is non-spontaneous. Positive $\Delta G$ means the process requires energy input to proceed.
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When is $\Delta G = \Delta G^\circ$ true?
When is $\Delta G = \Delta G^\circ$ true?
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When the reaction is at standard state conditions. Standard conditions mean all species at 1 M concentration or 1 atm pressure.
When the reaction is at standard state conditions. Standard conditions mean all species at 1 M concentration or 1 atm pressure.
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What does a negative $\Delta G$ indicate about a reaction?
What does a negative $\Delta G$ indicate about a reaction?
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The reaction is thermodynamically favorable. Negative $\Delta G$ means the process can occur spontaneously without external work.
The reaction is thermodynamically favorable. Negative $\Delta G$ means the process can occur spontaneously without external work.
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What is the significance of $\Delta G^\circ = 0$?
What is the significance of $\Delta G^\circ = 0$?
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The reaction is in equilibrium under standard conditions. Zero standard free energy means $K_{eq} = 1$ at standard conditions.
The reaction is in equilibrium under standard conditions. Zero standard free energy means $K_{eq} = 1$ at standard conditions.
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What happens to $\Delta G$ when a reaction is reversed?
What happens to $\Delta G$ when a reaction is reversed?
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The sign of $\Delta G$ is reversed. Reversing a reaction changes the sign of all thermodynamic quantities.
The sign of $\Delta G$ is reversed. Reversing a reaction changes the sign of all thermodynamic quantities.
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What is the standard state temperature for $\Delta G^\circ$ calculations?
What is the standard state temperature for $\Delta G^\circ$ calculations?
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$298 \text{ K}$. Standard temperature for thermodynamic calculations is 25°C or 298 K.
$298 \text{ K}$. Standard temperature for thermodynamic calculations is 25°C or 298 K.
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Identify the units of Gibbs free energy change, $\Delta G$.
Identify the units of Gibbs free energy change, $\Delta G$.
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Joules (J) or kilojoules (kJ). Energy units since $\Delta G$ represents energy change per mole of reaction.
Joules (J) or kilojoules (kJ). Energy units since $\Delta G$ represents energy change per mole of reaction.
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What is the expression for $\Delta S_{univ}$ in terms of $\Delta G$?
What is the expression for $\Delta S_{univ}$ in terms of $\Delta G$?
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$\Delta S_{univ} = -\frac{\Delta G}{T}$. This relates universal entropy change to Gibbs free energy change.
$\Delta S_{univ} = -\frac{\Delta G}{T}$. This relates universal entropy change to Gibbs free energy change.
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What is the relationship between $\Delta G$ and reaction rate?
What is the relationship between $\Delta G$ and reaction rate?
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$\Delta G$ does not affect reaction rate. $\Delta G$ determines thermodynamic favorability, not kinetic rate.
$\Delta G$ does not affect reaction rate. $\Delta G$ determines thermodynamic favorability, not kinetic rate.
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