化學問題!!!help!!

Cl2(g/aq) + 2e- → 2Cl-(aq)

這是一個還原半反應（half-reaction of reduction），並不會單獨進行，而必須要有另一個氧化半反應（half-reaction of oxidation）同時進行。故此，當 Cl2 遇到一個還原劑（reducing agent）時，以上半反應才會進行。

例如把氯水（chlorine water）加進溴化鉀溶液（potassium bromide solution）。氯水會被還原成氯離子（chloride ion），而溴化鉀溶液中的溴離子（bromide ion）會被氧化成溴溶液（bromine solution）。
Cl2(aq) + 2e- → 2Cl-(aq)
2Br-(aq) → Br2(aq) + 2e-
總反應式：Cl2(aq) + 2Br-(aq) → 2Cl-(aq) + Br2(aq)

要考慮是否進行反應，不應只考慮單一反應物的穩定性（stability），例如不應只考慮 Cl2 的穩定性。反應能夠進行，是因為生成物（products）整體上較反應物（reactants）穩定。

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Cl atom is much more reactive than Cl2 molecule. The outermost shell of Cl atom has 7 electrons, but the outermost shell of each Cl atom in Cl2 molecule has 8 electrons (a stable electronic configuration).


2007-04-06 16:15:28 補充：
The conversion of Cl2 to Cl^- involves the breaking of Cl-Cl covalent bond.It is rediculous to state that the Cl-Cl covalent bond is irrelevant.

This is redox reaction.
When Cl2 was reduced by reducing agent, Cl2 will gain 2 electron and become
Chloride ion.

This reaction is irrelevant to the properties of covanlent bond.
Therefore you can't use covanlent bond to elaborate this reaction.

2007-04-06 17:08:38 補充：
Hmmm...as you say,how the Cl-Cl covanlent bond related to the reaction?

2007-04-06 17:12:19 補充：
Michael,thanks for your remind!