8: Entropy and Gibbs Free Energy Flashcards

1
Q

What is entropy?

A

A measure of how much disorder or chaos there is.

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2
Q

What does it mean if something is high in entropy?

A

There is more disorder.

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3
Q

Which state of a substance would have the most entropy?
Why?

A

Gases, they have the most energy and are free to quickly move around.

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4
Q

Generally, how is entropy as a whole changing in the universe?
Give an example using a glass.

A

Entropy is always increasing.
For example, glass could shatter, increasing its entropy, but could never fit itself back together.

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5
Q

Give the formula for calculating entropy change.

A

S = entropy of products - entropy of reactants

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6
Q

Give the units for entropy.

A

J K-1 mol-1

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6
Q

Give the units for enthalpy change.

A

Kj-1 mol-1

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6
Q

What minimum Gibbs free energy value is usually required for a reaction to be feasible?

A

It must be 0 or negative.

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7
Q

Give the equation used to calculate enthalpy change.

A

Enthalpy change = products - reactants

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7
Q

What is gibbs free energy used for?

A

It predicts whether a reaction is feasible or not.

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7
Q

What is a feasible reaction?

A

A reaction that continues fully to completion.

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8
Q

What 2 factors, aside from a negative Gibbs free energy value, can affect reaction feasibility?

A

High activation energy
Slow rate of reaction

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8
Q

Give the equation for Gibbs free energy.

A

DeltaG = Delta H - TdeltaS

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9
Q

Give the formula for finding the temperature a reaction becomes feasible at.

A

T = enthalpy change / entropy change

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10
Q

If a reaction is exothermic, will enthalpy change be positive or negative?

A

Negative enthalpy change

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11
Q

If a reaction is endothermic, will the enthalpy change be positive or negative?

A

Positive enthalpy change

12
Q

If a reaction is exothermic (negative enthalpy change) and has a negative TdeltaS value, when will the reaction be feasible (high/low temperatures)
How do low and high temperatures effect the size of the entropy change?

A

It will be feasible at low temperatures
It will not be feasible at high temperatures.
Low temperatures will create a small positive entropy change.
High temperatures will create a a large positive entropy change

13
Q

If a reaction is exothermic (negative enthalpy change) and has a positive TdeltaS value, when will the reaction be feasible?

A

The reaction is always feasible as delta G is always negative.

14
Q

If a reaction is endothermic (positive enthalpy change) and has a negative TdeltaS value, when will the reaction be feasible?

A

The reaction is NEVER feasible, regardless of temperature as delta G is always positive.

15
Q

If a reaction is endothermic (positive enthalpy change) and has a positive TdeltaS value, when will the reaction be feasible? (high/low temperatures)
How do low/high temperatures effect the size of the entropy change?

A

The reaction will be feasible at high temperatures.
It is not feasible at low temperatures.
At high temperatures, the overall entropy change is a large negative number.
At low temperatures, the entropy change is a small negative number.

16
Q

How does higher temperature affect delta G and entropy change?

A

Higher temperature makes delta G more negative so entropy change gets bigger.