Relative Reactivities of Metals
Metals that displace H2 from water. MREs and a hot meal?.
Metals active enough to displace H2 from water lie below the
half-reaction for the reduction of water:
Metals that can displace other metals from solution.
Consider the reaction of sodium with water:
2 Na(s) 2 Na+(aq) + 2 e- -Eo = 2.71 V [oxidation]
2 H2O(l) + 2 e- H2 (g) + 2 OH-(aq) Eo = - 0.42 V [reduction]
2 Na(s) + 2 H2O(l) 2 Na+(aq) + H2(g) + 2 OH -(aq) Eocell = 2.29 V
Metals below others in Table 21.2, can replace them from solution:
Zn(s) Zn2+(aq) + 2 e- -Eo = 0.76 V [oxidation]
Fe2+(aq) + 2 e- Fe(s) Eo = - 0.44 V [reduction]
Zn(s) + Fe2+(aq) Zn2+(aq) + Fe(s) Eocell = 0.32 V
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