According to advertisements, “a diamond is forever.”

(a) Calculate $\Delta H^{\circ}, \Delta S^{\circ},$ and $\Delta G^{\circ}$ at 298 $\mathrm{K}$ for the phase change

(b) Given the conditions under which diamond jewelry is normally kept, argue for and against the statement in the ad.

(c) Given the answers in part (a), what would need to be done to make synthetic diamonds from graphite?

(d) Assuming $\Delta H^{\circ}$ and $\Delta S^{\circ}$ do not change with temperature, can graphite be converted to diamond spontaneously at 1 $\mathrm{atm} ?$

## Discussion

## Video Transcript

No transcript available

## Recommended Questions

Consider the reaction 2 $\mathrm{NO}_{2}(g) \longrightarrow \mathrm{N}_{2} \mathrm{O}_{4}(g) .(\mathbf{a})$ Using data from Appendix $\mathrm{C},$ calculate $\Delta G^{\circ}$ at 298 $\mathrm{K}$ . (b) Calculate $\Delta G$ at 298 $\mathrm{K}$ if the partial pressures of $\mathrm{NO}_{2}$ and $\mathrm{N}_{2} \mathrm{O}_{4}$ are 0.40 atm and 1.60 atm, respectively.

Free Energy and Equilibrium (Section)

Consider the reaction 2 $\mathrm{NO} 2(g) \rightarrow \mathrm{N} 2 \mathrm{O} 4(g) .$ (a) Using data from Appendix C, calculate $\Delta G^{\circ}$ at 298

$\mathrm{K}$ (b) Calculate $\Delta G$ at 298 $\mathrm{K}$ if the partial pressures of $\mathrm{NO} 2$ and $\mathrm{N} 2 \mathrm{O} 4$ are 0.40 atm and 1.60

atm, respectively.

Methanol $\left(\mathrm{CH}_{3} \mathrm{OH}\right)$ can be made by the controlled oxidation of methane:

$$

\mathrm{CH}_{4}(g)+\frac{1}{2} \mathrm{O}_{2}(g) \longrightarrow \mathrm{CH}_{3} \mathrm{OH}(g)

$$

(a) Use data in Appendix C to calculate $\Delta H^{\circ}$ and $\Delta S^{\circ}$ for this reaction. (b) Will $\Delta G$ for the reaction increase, decrease, or stay unchanged with increasing temperature?

(c) Calculate $\Delta G^{\circ}$ at 298 $\mathrm{K}$ . Under standard conditions, is the reaction spontaneous at this temperature? Is there a temperature at which the reaction would be at

equilibrium under standard conditions and that is low enough so that the compounds involved are likely to be stable?