1. The problem statement, all variables and given/known data http://www.physics.ox.ac.uk/olympiad/Downloads/PastPapers/BPhO_PC_2006_QP.pdf Q15b Answers: http://www.physics.ox.ac.uk/olympiad/Downloads/PastPapers/BPhO_PC_2006_MS.pdf I am confused on how the answer is reached, specifically how the formula energy needed=power/rate of reduction is laid out 2. Relevant equations energy needed = power/rate of reduction 3. The attempt at a solution What I am confused about is that since power is in J/s and rate of reduction is in kg/s that would make Energy needed into J/kg... or specific heat capacity and not energy itself. How does this work?