A voltaic cell is constructed from a standard Ni2+|Ni half cell (E°red = -0.250V) and a standard Fe3+|Fe2+ half cell (E°red = 0.
771V). (Use the lowest possible coefficients. Use the pull-down boxes to specify states such as (aq) or (s). If a box is not needed, leave it blank.) The anode reaction is:
Looking at the values of reduction potential given in the question, Ni2+|Ni half cell has a more negative reduction potential than the Fe3+|Fe2+ half cell. The more negative the reduction potential of a half cell, the more its tendency to act as the anode. Hence based on the half cell reduction potentials presented in the question, Ni2+|Ni is the anode while the other is the cathode.
The compound is made of 2 oxygen molecules and the oxygen made of 20.61% its mass. If the molar mass of oxygen is 16, the molar mass of the compound will be:
2* oxygen* (16g/mol / oxygen) = 20.61% compound mass
