Is Fe^2+(aq) and Cu(s) a spontaneous redox reaction in a voltaic cell
Yes, Fe^2+(aq) and Cu(s) can form a spontaneous redox reaction in a voltaic cell. Fe^2+(aq) can act as the reducing agent and Cu(s) can act as the oxidizing agent. During the reaction, Fe^2+(aq) will lose electrons to be oxidized to Fe^3+(aq), and Cu(s) will gain those electrons to be reduced to Cu^2+(aq).
The overall redox reaction can be represented as:
Fe^2+(aq) + Cu(s) → Fe^3+(aq) + Cu^2+(aq)
The standard reduction potentials of Cu^2+(aq)/Cu(s) (+0.34 V) is larger than the standard reduction potential of Fe^3+(aq)/Fe^2+(aq) (+0.77 V). Since the standard reduction potential of Cu^2+(aq)/Cu(s) is larger, it means that it has a higher tendency to be reduced. Therefore, the reaction is spontaneous, and it can produce an electrical current in a voltaic cell.