Final answer:
The minimum energy to free a hydrogen atom from water corresponds to the ionization energy of hydrogen in its ground state, which is 13.6 eV.
Step-by-step explanation:
The minimum energy required to free a hydrogen atom from water is related to the ionization energy of hydrogen in its ground state. The ionization energy is the energy needed for an electron to go from being bound to an atom to being completely free of that atom. According to the question, we are looking for the minimum energy required to ionize hydrogen, which experimentally is 13.6 eV. This is the energy needed to ionize a hydrogen atom when its electron is at the ground state (n=1). If the electron occupies a higher energy state, like n=4, less energy is required to ionize it, but the question asks for the minimum energy to do any ionization, which still corresponds to the ground state ionization energy of hydrogen.