Marine organisms have shells which are made of biologically secreted calcium carbonate (CaCO3, molecular weight: 100 g/mol). These shells are predominantly in the crystalline form calcite, while there are two other crystalline forms (polymorphs) of CaCO3 called aragonite and vaterite. Some parameters at 298 K and 1 atm are tabulated below. The phase diagram of the three is also shown where pressure is in kilobars (1 bar is approximately 1 atm). ARAGONITE Aragonite Calcite -1207.0 -1206.9 CALCITE Property Heat of formation (kJ/mol) Gibbs free energy of formation (kJ/mol) Density (g/cm) -1127.7 -1128.8 2.93 2.71 VATERITE 200 250 300 389 Tix) (a) Write the equation of the reaction for the calcite to aragonite conversion. (b) Do you expect to find aragonite or calcite in shells of fossils of these organisms that died eons ago? Explain based on the tabulated values. (c) If you find some fossils which have aragonite shells, calculate the pressure that these fossils must have been subjected to for these shells to have turned into aragonite. (d) At 1 atm, can one raise the temperature to convert calcite into aragonite? Explain based on the thermodynamic data and/or the figure presented. (e) What is the range of density values of vaterite; is it larger than 2.93, less than 2.71 or a value in between the two? Explain to get any credit