Final answer:
Calculating the exact pressure needed for the transformation of graphite to diamond requires specific thermodynamic data, but the transition starts at pressures around 5 GPa and is often completed by 10 GPa.
Step-by-step explanation:
The question asks to calculate the pressure needed to transform graphite to diamond at room temperature (298 K) at equilibrium. According to the phase diagram for carbon, at ambient atmospheric pressure, graphite is the stable form, whereas diamond becomes stable at very high pressures during its geological formation.
While the specific calculation is not provided in the reference material, generally such transformations require pressures in the gigapascal (GPa) range. High-pressure research suggests that the transition from graphite to diamond starts at pressures around 5 GPa and is typically completed by around 10 GPa depending on the temperature.