To calculate the amount of energy needed to desorb 10 moles of hydrogen gas from a metal surface, we can use the following formula:Energy = moles enthalpy of desorptionGiven that the enthalpy of desorption is -120 kJ/mol, we need to reverse the sign to find the energy needed to desorb the hydrogen gas. So, the enthalpy of desorption becomes +120 kJ/mol.Now, we can plug in the values:Energy = 10 moles 120 kJ/molEnergy = 1200 kJTherefore, 1200 kJ of energy is needed to desorb 10 moles of hydrogen gas from the metal surface.