91Ó°ÊÓ

Explain why the units for entropy have a dependence on temperature- for example, why are the units \(\mathrm{J} \mathrm{mol}^{-1} \mathrm{~K}^{-1}\) ?

Explain why the values of \(\Delta H\) for elements in their standard state are \(0 \mathrm{~kJ} \mathrm{~mol}^{-1}\), but the values for the standard entropy, \(S,\) for elements are \(\operatorname{not} 0 \mathrm{~J} \mathrm{~mol}^{-1} \mathrm{~K}^{-1}\).

Would you expect the entropy of an alloy (a solution of two metals) to be zero at \(0 \mathrm{~K}\) ? Explain your answer.

What is the equation expressing the change in the Gibbs free energy for a reaction occurring at constant temperature and pressure?

Why can \(\Delta G^{\circ}\) be calculated at different temperatures using \(\Delta H^{\circ}\) and \(\Delta S^{\circ}\) at \(298.15 \mathrm{~K}\) ?

How is free energy related to useful work?

What is a thermodynamically reversible process? How is the amount of work obtained from a change related to thermodynamic reversibility?

In what way is free energy related to equilibrium?

Considering the fact that the formation of a bond between two atoms is exothermic and is accompanied by an entropy decrease, explain why all chemical compounds decompose into individual atoms if heated to a high enough temperature.

Sketch the shape of the free energy curve for a chemical reaction that has a positive \(\Delta G^{\circ}\). Indicate the composition of the reaction mixture corresponding to equilibrium.