91Ó°ÊÓ

What is a spontaneous process? Give three examples of spontaneous processes. Give three examples of nonspontaneous processes.

Which contains greater entropy, a quantity of frozen benzene or the same quantity of liquid benzene at the same temperature? Explain in terms of the dispersal of energy in the substance.

State the second law of thermodynamics.

The entropy change \(\Delta S\) for a phase transition equals \(\Delta H / T\), where \(\Delta H\) is the enthalpy change. Why is it that the entropy change for a system in which a chemical reaction occurs spontaneously does not equal \(\Delta H / T\) ?

Describe what you would look for in a reaction involving gases in order to predict the sign of \(\Delta S^{\circ}\). Explain.

Define the free energy \(G\). How is \(\Delta G\) related to \(\Delta H\) and \(\Delta S\) ?

What is meant by the standard free-energy change \(\Delta G^{\circ}\) for a reaction? What is meant by the standard free energy of formation \(\Delta G_{f}^{\circ}\) of a substance?

Explain how \(\Delta G^{\circ}\) can be used to decide whether a chemical equation is spontaneous in the direction written.

What is the useful work obtained in the ideal situation in which a chemical reaction with free-energy change \(\Delta G\) is run so that it produces no entropy?

How is the concept of coupling of reactions useful in explaining how a nonspontaneous change could be made to occur?