To calculate the enthalpy change of ionization for hydrogen gas when one mole of H2 gas is ionized to form two moles of H+ ions in the gas phase, we need to consider the following reaction:H2 g 2H g First, we need to break the H2 molecule into two H atoms. The bond dissociation energy for H2 is approximately 436 kJ/mol. So, the enthalpy change for this step is:H1 = +436 kJ/molNext, we need to ionize each H atom to form H+ ions. The enthalpy change of ionization for H g is given as +1312 kJ/mol. Since we have two H atoms, the enthalpy change for this step is:H2 = 2 +1312 kJ/mol = +2624 kJ/molNow, we can calculate the total enthalpy change for the ionization of one mole of H2 gas:H_total = H1 + H2 = +436 kJ/mol + +2624 kJ/mol = +3060 kJ/molTherefore, the enthalpy change of ionization for hydrogen gas when one mole of H2 gas is ionized to form two moles of H+ ions in the gas phase is +3060 kJ/mol.