Final answer:
ATP hydrolysis has a negative ΔG° due to it being an exergonic reaction that releases energy as ATP breaks down into ADP and a phosphate group. This release of energy is favored by the instability of ATP molecules and the repulsion between negatively charged phosphate groups.
Step-by-step explanation:
ATP hydrolysis has a negative ΔG° because it is an exergonic reaction, meaning it releases energy. The process involves the hydrolysis of ATP to ADP and a phosphate group, which breaks the high-energy bond holding the last phosphate group, releasing energy in the process. This release of energy is approximately -7 Kcal/mole under standard conditions, but can reach about -14 kcal/mole in cellular conditions due to the instability of ATP molecules and repulsion between negatively charged phosphate groups. This instability and repulsion create a state where the energy required to keep the phosphate groups together is higher than the energy state once they are released, which naturally favors the hydrolysis reaction, leading to a lowering of free energy or a negative ΔG°.