In the reaction of two moles of gaseous hydrogen and one mole of gaseous oxygen to form two moles of gaseous water vapor, two moles of products are formed from three moles of reactants. If this reaction is done at 1.01 × 10⁵ Pa (and at 0°C), the volume is reduced by 22.4 L. 

(a) In this reaction, how much work is done on the system (H₂, O₂, H₂O) by the surroundings? 

(b) The enthalpy change for this reaction is −483.6 kJ. Use this value, along with the answer to (a), to calculate ∆_rU, the change in internal energy in the system.