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Chapter 18: Problem 15

Define free energy. What are its units?

Short Answer

Expert verified
Free energy is the amount of energy in a system that is available to do work in constant temperature and pressure. It is typically measured in Joules (J) in the SI.

Step by step solution

01

Define Free Energy

Free energy is a thermodynamic quantity equivalent to the capacity of a system to do work. Specifically, it is the amount of energy that can be converted into work at a constant temperature and pressure. It can be calculated using the equation \(G = H - TS\), where \(G\) is the Gibbs free energy, \(H\) is the enthalpy, \(T\) is the absolute temperature, and \(S\) is the entropy.
02

Units of Free Energy

Free energy is usually measured in Joules (J) in the International System of Units (SI). But it can also be represented in calories (cal), kilocalories (kcal), or as electron volts(eV).

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Most popular questions from this chapter

Explain the following nursery rhyme in terms of the second law of thermodynamics. Humpty Dumpty sat on a wall; Humpty Dumpty had a great fall. All the King's horses and all the King's men Couldn't put Humpty together again.

Consider the following facts: Water freezes spontaneously at \(-5^{\circ} \mathrm{C}\) and \(1 \mathrm{~atm},\) and ice has a more ordered structure than liquid water. Explain how a spontaneous process can lead to a decrease in entropy.

(a) Over the years there have been numerous claims about "perpetual motion machines," machines that will produce useful work with no input of energy. Explain why the first law of thermodynamics prohibits the possibility of such a machine existing. (b) Another kind of machine, sometimes called a “perpetual motion of the second kind," operates as follows. Suppose an ocean liner sails by scooping up water from the ocean and then extracting heat from the water, converting the heat to electric power to run the ship, and dumping the water back into the ocean. This process does not violate the first law of thermodynamics, for no energy is created-energy from the ocean is just converted to electrical energy. Show that the second law of thermodynamics prohibits the existence of such a machine.

State the third law of thermodynamics and explain its usefulness in calculating entropy values.

State the second law of thermodynamics in words and express it mathematically.
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