AP Chemistry: Thermodynamics flashcards

Question 1

What is entropy (S) a measure of?

Accepted Answer

How widely matter and/or energy is spread out within a system. It depends on the number of microstates and is often called disorder.

Question 2

Is entropy a state function?

Accepted Answer

Yes. Entropy (S) is a state function.

Question 3

What is a microstate?

Accepted Answer

One of the possible ways the matter and energy in a system can be arranged.

Question 4

What is a spontaneous process?

Accepted Answer

One that proceeds with no ongoing energy supply from outside the system.

Question 5

What is a reversible process?

Accepted Answer

A process that runs so slowly that an infinitesimally small change in conditions can make it reverse direction.

Question 6

Can a real process be perfectly reversible?

Accepted Answer

No. A reversible process is a hypothetical construct that real processes can only approximate.

Question 7

State the second law of thermodynamics in terms of the entropy of the universe.

Accepted Answer

All spontaneous processes increase the entropy of the universe.

Question 8

State the third law of thermodynamics.

Accepted Answer

A perfect crystal at 0 K (absolute zero) has zero entropy.

Question 9

Why does a flawless pure crystal at 0 K have zero entropy?

Accepted Answer

It has just one possible microstate.

Question 10

What is standard entropy (S°)?

Accepted Answer

Entropy per mole of a substance at 1 bar; tables usually give values measured at 298.15 K.

Question 11

What is the standard entropy change (ΔS°) for a reaction?

Accepted Answer

The entropy change for the reaction, calculated from the standard entropies.

Question 12

What is the standard free energy of formation?

Accepted Answer

The free energy change when one mole of a substance forms from its elements in their standard states.

Question 13

What does the standard free energy change (ΔG°) describe?

Accepted Answer

The free energy change when a process runs at standard conditions: gases at 1 bar, solutions at 1 M.

Question 14

What do all spontaneous processes do to the Gibbs free energy (G)?

Accepted Answer

They decrease it.

Question 15

In terms of which system properties is Gibbs free energy defined?

Accepted Answer

Enthalpy and entropy.

Question 16

What does Delta S_univ < 0 mean for a process?

Accepted Answer

The process is nonspontaneous.

Question 17

What does a negative value of Delta G indicate?

Accepted Answer

A spontaneous process.

Question 18

What does a positive value of Delta G indicate?

Accepted Answer

A nonspontaneous process.

Question 19

What does Delta G = 0 indicate?

Accepted Answer

The system is at equilibrium.

Question 20

Entropy can be related to what ratio, besides the number of microstates?

Accepted Answer

The ratio of reversible heat to the kelvin temperature.

Question 21

Write the equation relating entropy change to reversible heat and temperature.

Accepted Answer

Delta S = q_rev / T

Question 22

Write the Boltzmann entropy equation given in the key equations.

Accepted Answer

S = k ln W

Question 23

Write the equation for the entropy change of the universe.

Accepted Answer

Delta S_univ = Delta S_sys + Delta S_surr

Question 24

Write the equation for the standard entropy change of a reaction from standard entropies.

Accepted Answer

Delta S° = sum of nu S°(products) - sum of nu S°(reactants)

Question 25

Write the equation for the Gibbs free energy change in terms of enthalpy and entropy changes.

Accepted Answer

Delta G = Delta H - T Delta S

AP Chemistry: Thermodynamics flashcards

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