Chapter 5, Problem 123AP

For reactions in condensed phases ( liquids and solids), the difference between $\Delta H$ and $\Delta U$ is usually quite small. This statement holds for reactions carried out under atmospheric conditions. For certain geochemical processes, however, the external pressure may be so great that $\Delta H$ and $\Delta U$ At can differ by a significant amount. A well known example it the slow conversion of graphite to diamond under Earth's surface Calculate $\Delta H-\Delta U$ for the conversion of 1 mole of graphite to t mole of diamond at a pressure of 50.000 atm. The densities of graphite and diamond are $\text{ 2}\text{. 25g/}{\text{m}}^{\text{2}}\text{and 3}\text{.52 g/c}{\text{m}}^{\text{2}}$, respectively.