To determine the enthalpy of adsorption for the reaction of hydrogen gas adsorbing onto a platinum surface, we can use the following equation:H_ads = U_ads + PVwhere H_ads is the enthalpy of adsorption, U_ads is the internal energy change, P is the pressure, and V is the change in volume.First, we need to find the moles of hydrogen gas adsorbed. The molar mass of hydrogen gas H2 is 2.016 g/mol.moles of H2 = 2.00 g / 2.016 g/mol = 0.9921 molNext, we need to find the initial and final volumes of the hydrogen gas. Since the initial volume is given as 1.00 L, we can use the ideal gas law to find the initial moles of hydrogen gas:PV = nRTwhere P is the pressure 1 bar = 100,000 Pa , V is the volume 1.00 L = 0.001 m , n is the moles of hydrogen gas, R is the ideal gas constant 8.314 J/ molK , and T is the temperature 25C = 298.15 K . 100,000 Pa 0.001 m = n 8.314 J/ molK 298.15 K n = 0.0404 molThe final moles of hydrogen gas are the initial moles plus the moles adsorbed:n_final = 0.0404 mol + 0.9921 mol = 1.0325 molNow we can find the final volume using the ideal gas law:V_final = nRT/PV_final = 1.0325 mol 8.314 J/ molK 298.15 K / 100,000 Pa V_final = 0.001025 m = 1.025 LThe change in volume is:V = V_final - V_initial = 1.025 L - 1.00 L = 0.025 L = 0.000025 mNow we need to find the internal energy change U_ads . Since the platinum surface is in thermal equilibrium with the surroundings, there is no temperature change, and the internal energy change is zero:U_ads = 0Finally, we can find the enthalpy of adsorption:H_ads = U_ads + PVH_ads = 0 + 100,000 Pa 0.000025 m H_ads = 2.5 JThe enthalpy of adsorption for the reaction of hydrogen gas adsorbing onto a platinum surface is 2.5 J.