Oxidation-Reduction

 

34) The reason for each of the choices below is the same. The more readily a substance is oxidized (the more negative the E°red or the more positive the E°ox ) the stronger the reducing agent.

 

      (a) Fe2+(aq) + 2e- Fe(s)              E°red = -0.440 V

           Mg2+(aq) + 2e- Mg(s)           E°red = -2.37 V

           Mg(s) is the better reducing agent.

 

      (b) Ca2+(aq) + 2e- Ca(s)              E°red = -2.87 V

           Al3+(aq) + 3e- Al(s)                 E°red = -1.66 V

           Ca(s) is the better reducing agent.

 

      (c) 2H+(aq) + 2e- H2(g)                               E°red = 0.000 V

           S(s) + 2H+(aq) + 2e- H2S(g)                  E°red = +0.141 V

           H2(g) is the better reducing agent.

 

      (d) HSO4- (aq) + 3H+ + 2e- H2SO3(aq) + H2O(l)                             E°red = +0.17 V

           2CO2(g) + 2H+(aq) + 2e- H2C2O4(aq)                                         E°red = -0.49 V

           H2C2O4(aq) is the better reducing agent.