The change in molar internal energy when CaCO3(s) as calcite converts to another
form, aragonite, is +0.21 kJ mol−1. Calculate the difference between the molar
enthalpy and internal energy changes when the pressure is 1.0 bar given that the
densities of the polymorphs are 2.71 g cm−3 and 2.93 g cm−3, respectively.