Gibbs Free Energy Standard Conditions Quiz

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Questions and Answers

Which of the following is not a limitation of the 1st Law of Thermodynamics?

It does not tell us the direction of heat flow.

It does not account for the conservation of energy. (correct)

It is impossible to convert internal energy completely into work done.

It does not distinguish between spontaneous and non-spontaneous processes.

Which of the following is a characteristic of an irreversible process?

It can be reversed by an infinitesimal change in external conditions.

The system remains in thermodynamic equilibrium throughout the process.

It can be completely reversed by itself.

It always proceeds in one direction. (correct)

A reversible process is an idealization and cannot happen in real systems.

True

What does Clausius's statement of the 2nd Law of Thermodynamics imply?

Heat cannot spontaneously flow from a colder body to a warmer body without work. Signup and view all the answers

What does Kelvin's statement of the 2nd Law of Thermodynamics say?

It is impossible to convert heat from a single source completely into work. Signup and view all the answers

What is the name given to a device that converts heat partially into mechanical work?

Heat engine Signup and view all the answers

Which of the following is true about the efficiency of a heat engine?

It is the ratio of the energy gotten out to the energy put in. Signup and view all the answers

Which of the following best describes the concept of entropy?

A measure of the disorder or randomness of a system. Signup and view all the answers

According to the 2nd Law of Thermodynamics, the entropy of the universe is always increasing.

True Signup and view all the answers

What does the 3rd Law of Thermodynamics state?

The entropy of all perfect crystalline substances is zero at absolute zero (T = 0 K). Signup and view all the answers

Which of the following is not a factor affecting entropy?

Volume of the system Signup and view all the answers

In terms of thermodynamics, what is Gibbs Free Energy a measure of?

The energy available to the system to do useful work Signup and view all the answers

A process with a negative Gibbs Free Energy change (ΔG < 0) is considered spontaneous.

True Signup and view all the answers

What is Hess's Law used to calculate?

The standard enthalpy of an overall reaction Signup and view all the answers

Which of the following statements is true about the standard enthalpy of formation?

It is the enthalpy change for the formation of one mole of a compound from its elements in their standard states. Signup and view all the answers

Study Notes

Limitations of the 1st Law of Thermodynamics

The first law does not differentiate between spontaneous and non-spontaneous processes.
It does not indicate the direction of heat flow.
It's impossible to completely convert internal energy into work.
The total energy of the universe remains constant: ∆U = q + w, ΔΕsys + ΔΕsurr = ΔΕuniv = 0
ΔΕsys = -ΔΕsurr

The 2nd Law of Thermodynamics

Used to classify thermodynamic processes into:
- Irreversible (natural/spontaneous): e.g., rusting, rolling rock
- Reversible: equilibrium processes, system always at thermodynamic equilibrium
- Impossible: processes that violate the 2nd law

Spontaneous Processes

Proceed automatically without external work.
The opposite of a spontaneous process is a non-spontaneous process.
A non-spontaneous process requires external work to occur.

The 2nd Law of Thermodynamics (continued)

The opposite of irreversible processes cannot occur automatically without external work.
Impossible processes violate the 2nd law.
Examples of impossible processes include a cup of coffee warming up a cooler room, or a machine converting heat entirely into work.

Impossible Processes

Processes that cannot occur naturally.
They violate the second law of thermodynamics.

Reversible Processes

A system experiencing a reversible process can return to its original conditions by reversing the process exactly.
Reversible processes are equilibrium processes.
The system always remains in thermodynamic equilibrium.
There is no heat flow into or out of the system.
The system does not perform work against its surroundings.
Changes occur in infinitely small steps, remaining in equilibrium at each stage. This is an idealized concept.

Clausius' Statement (Refrigerators)

Energy does not flow spontaneously from a colder body to a warmer body without work being done.

Kelvin Statement

It is impossible to take heat from a single source and completely convert it into work.

Heat Engine

Device that converts heat partially into mechanical work.
Absorbs heat from a hot reservoir, does work, and rejects heat to a cold reservoir.
Efficiency is the ratio of work output to heat input. η=W/QH = (QH-QC)/QH = 1-QC/QH η = (TH-TC)/TH= 1-(TC/TH)

Maximum Efficiency

Efficiency is maximized when the ratio of low temperature to high temperature is minimized.
η = (TH-TC)/TH.

Refrigerator

Works on the reverse principle of heat engines.
Absorbs heat from a colder region and expels it to a hotter region.
Requires external work to occur.

Entropy and the Second Law of Thermodynamics

Entropy is a measure of a system's disorder.
Natural processes tend toward greater disorder.
Natural processes increase entropy.
The only way to decrease a system's entropy is to perform work.
All spontaneous changes increase the total entropy of the universe.

Entropy as a State Function

The overall change in entropy when a system (or the universe) returns to its initial state is zero.

2nd Law of Thermodynamics (additional statements)

Entropy changes for a reversible process in an isolated system is zero
Entropy changes for an irreversible process in an isolated system is greater than zero.

The Third Law of Thermodynamics

Entropy of a perfect crystal at absolute zero is zero
No physical process can cool a system to absolute zero in a finite number of steps
Absolute zero temperature cannot be reached.