Term
Second Law of Thermodynamics |
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Definition
For any spontaneous process, the entropy of the universe increases (◊Suniv>0)
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Term
Entropy increases (◊S>0) for each of the following: |
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Definition
The phase transition from a solid to a liquid
The phase transition from a solid to a gas
The phase transition from a liquid to a gas
An increase in the number of moles of a gas during a chemical reaction |
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Term
Entropy of the universe, system, and surroundings |
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Definition
◊Suniv= ◊Ssys + ◊Ssurr
The entropy of the universe must increase (◊Suniv>0) for a process to be spontaneous. The entropy of the system could therefore decrease (◊Ssys<0) as long as the entropy of the surroundings increases by a greater amound (◊Ssurr> -◊Ssys) |
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Term
◊Ssurr = -◊Hsys
T
(at constant T and P) |
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Definition
◊Ssurr = -◊Hsys
T
(at constant T and P) |
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Term
◊G = ◊H - T◊S |
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Definition
◊G = ◊H - T◊S |
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Term
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Definition
A decrease in Gibbs free energy (◊G < 0) corresponds to a spontaneous process
An increase in Gibbs free energy (◊G > 0) corresponds to a nonspontaneous process |
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Term
When ◊H is negative and ◊S is positive, is the reaction spontaneous or nonspontaneous? |
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Definition
It is spontaneous at all temperatures |
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Term
When ◊H is positive and ◊S is negative, is the reaction spontaneous or nonspontaneous? |
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Definition
It is nonspontaneous at all temperatures |
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Term
When ◊H and ◊S are both negative, is the reaction spontaneous or nonspontaneous? |
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Definition
It is spontaneous at low temperatures, but nonspontaneous at high temperatures. |
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Term
When ◊H and ◊S are both positive, is the reaction spontaneous or nonspontaneous? |
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Definition
It is nonspontaneous at low temperatures, and spontaneous at high temperatures. |
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Term
The standard state of a substance is defined as follows: |
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Definition
For a gas: The standard state for a gas is the pure gas at a pressure of exactly 1 atm.
For a liquid or solid: The standard state for a liquid or solid is the pure substance in its most stable form at a pressure of 1 atm and the temperature of interest (often taken to be 25 C)
For a Substance in Solution: The standard state for a substance in solution is a concentration of exactly 1M. |
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Term
Entopies of gases, liquids, and solids: |
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Definition
The entropy of a gas is generally greater than a liquid, which is in turn greater than the entropy of a solid.
gas>liquid>solid |
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Term
Entopies related to molar mass: |
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Definition
Entropy increases with increasing molar mass. |
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Term
Entropies related to molar complexity: |
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Definition
Entropy generally increases with increasing molar complexity
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Term
Entropies related to dissolution: |
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Definition
The dissolution of a crystalline solid into solution usually results in an increase in entropy. |
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Term
Determining ◊G°rxn for a stepwise reaction from the changes in free energy for each of the steps |
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Definition
If a chemical equation is multiplied by some factor, then ◊Grxn is also multiplied by the same factor
If a chemical equation is reversed, then ◊Grxn changes sign
If a chemical equation can be expressed as the sum of a series of steps, then ◊Grxn for the overall equation is the sum of the free energies of reactions for each step.
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Term
The free energy change of a reaction under nonstandard conditions (◊Grxn) |
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Definition
◊Grxn = ◊G°rxn + RTlnQ |
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Term
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Definition
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