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Questions and Answers
What does the Third Law of Thermodynamics state about the entropy of a perfectly crystalline substance at 0 K?
What does the Third Law of Thermodynamics state about the entropy of a perfectly crystalline substance at 0 K?
In standard state conditions, what is typically the temperature used when determining standard absolute entropies?
In standard state conditions, what is typically the temperature used when determining standard absolute entropies?
Which state of matter has the highest relative standard entropy at a given temperature?
Which state of matter has the highest relative standard entropy at a given temperature?
How does molar mass affect the entropy of a substance?
How does molar mass affect the entropy of a substance?
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What can be concluded about the relative standard entropies of different allotropes?
What can be concluded about the relative standard entropies of different allotropes?
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What is true about the entropy of dissolved solids compared to their undissolved counterparts?
What is true about the entropy of dissolved solids compared to their undissolved counterparts?
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What is the effect of molecular complexity on standard entropy?
What is the effect of molecular complexity on standard entropy?
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Which characteristic of a system can indicate that a process will be spontaneous?
Which characteristic of a system can indicate that a process will be spontaneous?
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Under what conditions will Gibbs Free Energy, G, be negative?
Under what conditions will Gibbs Free Energy, G, be negative?
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When is a reaction considered to be spontaneous in terms of G° and K?
When is a reaction considered to be spontaneous in terms of G° and K?
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What does it mean when G = 0 in terms of the reaction?
What does it mean when G = 0 in terms of the reaction?
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Which statement accurately describes the relationship between G° and the reaction quotient Q?
Which statement accurately describes the relationship between G° and the reaction quotient Q?
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Which conditions imply that G° is positive?
Which conditions imply that G° is positive?
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What contributes to the standard free energy change G°?
What contributes to the standard free energy change G°?
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How does the thermodynamic equilibrium constant K behave with temperature changes?
How does the thermodynamic equilibrium constant K behave with temperature changes?
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What must be true about all reactants and products for G = G°?
What must be true about all reactants and products for G = G°?
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What happens to the standard free energy change (G°) of a reaction when it is spontaneous?
What happens to the standard free energy change (G°) of a reaction when it is spontaneous?
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Which statement accurately describes the free energy (G) in thermodynamics?
Which statement accurately describes the free energy (G) in thermodynamics?
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What is the value of the standard free energy of formation (Gf°) for elements in their most stable states?
What is the value of the standard free energy of formation (Gf°) for elements in their most stable states?
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During a reaction, if free energy decreases, what other thermodynamic quantity is likely increasing?
During a reaction, if free energy decreases, what other thermodynamic quantity is likely increasing?
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What defines a reaction where G° has a small negative value?
What defines a reaction where G° has a small negative value?
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Why is the energy termed 'free' in free energy?
Why is the energy termed 'free' in free energy?
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In which situation is a reaction considered nonspontaneous based on standard free energy change?
In which situation is a reaction considered nonspontaneous based on standard free energy change?
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What occurs when a system has more energy states available during a reaction?
What occurs when a system has more energy states available during a reaction?
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Study Notes
Free Energy (G)
- Free energy (G) is calculated using the formula G = H – TS, linking enthalpy (H), temperature (T), and entropy (S).
- A negative G indicates a spontaneous reaction, while a positive S contributes to a negative G.
Standard Free Energy of Formation, Gf°
- Gf° measures free-energy change when 1 mole of substance forms from its elements at standard conditions (1 atm, specified temperature).
- Elements in their most stable state have a Gf° value of zero.
Spontaneity of a Reaction using G°
- A large negative G° signifies that the reaction is spontaneous, with near-complete transformation from reactants to products.
- A large positive G° indicates nonspontaneity, meaning reactants yield minimal products.
- Small positive or negative G° suggests an equilibrium scenario with significant amounts of both reactants and products.
Concept of "Free" Energy
- Free energy is the maximum energy available to perform work from a system.
- In exothermic reactions, some released heat increases surrounding entropy, reducing work availability.
Free Energy Change During a Reaction
- A decrease in free energy can result in work done and an increase in entropy.
Gibbs Free Energy, G
- G is negative for spontaneous processes under conditions:
- Negative H and positive S (exothermic, increased disorder).
- Negative large H and small negative S.
- Positive small H and large positive S, or high temperature.
- G is positive when H is positive and S negative (never spontaneous).
Relating G° to the Equilibrium Constant, K
- G equals G° only at standard states (1 atm for gases, 1 M for solutes).
- Under nonstandard conditions, the equation is G = G° + RT ln Q; at equilibrium, G = 0, which relates G° and K: G° = -RT ln K.
Thermodynamic Equilibrium Constant, K
- K is derived from concentrations expressed as partial pressures (gases) or molarities (solutions) at standard conditions.
Spontaneity using G° and K
- At equilibrium (G = 0), if K > 1, G° is negative, indicating spontaneity; K < 1 means G° is positive, indicating nonspontaneity.
Third Law of Thermodynamics
- A perfectly crystalline substance at 0 K has zero entropy; all other substances possess positive entropy.
Standard Absolute Entropies, S°
- S° represents standard state conditions, defining entropy for 1 mole of a substance typically at 298 K.
Relative Standard Entropies: States
- Gases have greater entropy than liquids, and liquids have greater entropy than solids at a corresponding temperature.
Relative Standard Entropies: Molar Mass
- Higher molar mass correlates with larger entropy due to closely spaced energy states.
Relative Standard Entropies: Allotropes
- Less constrained structures (e.g., graphite) exhibit higher entropy.
Relative Standard Entropies: Dissolution
- Dissolved solids usually possess higher entropy due to particle distribution throughout mixtures.
Relative Standard Entropies: Molecular Complexity
- Larger, more complex molecules generally have increased entropy compared to simpler structures.
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Description
Explore the concepts of free energy and its relation to thermodynamics. This quiz covers essential principles such as the equation G = H - TS and the spontaneity of reactions. Test your understanding of standard free energy changes and their implications in chemical processes.
