點解high temperture 同 有海水 會加快rusting

A reaction that can go to completion require many steps.
eg: Rusting requires ionization of Fe atom to form Fe 2+
Fe ------> Fe 2+ + 2e-
Atomization breaks the covalent bond between oxygen molecules to form oxygen atoms.
O2 -------> 2O
However, these processes require energy (endothermic).
These energy required before the reaction start are named activation energy.

In high temp situation, temp provides some energy to the molecules
to break some of the bonds which it can speed up the reaction rate.
More molecules can overcome the activation energy.
Hence, more molecules are ready to start the reaction.

Also, if you study physics, you should know the kinetic energy increase with
the temp. As the KE of the molecules increase, the molecules move faster,
therefore, more successful collision is made.
The reaction rate increase and the iron rust faster.

Sea water contain NaCl and others ions. The solution can be called electrolyte.
Rusting is the formation of iron oxide, which involve e- transfer from iron to oxygen. Since electrolyte contain mobile ions that can help to transfer e-.
The presence of sea water (electrolyte) speed up the rusting.

hope can help u ^^~

2008-03-25 23:47:16 補充：
Electrolytes provide materials to complete the electric circuit like the salt bridge between two beakers in electrolysis.
In fact, most ionic compounds can give similar action of sea water given that they are soluble in water and act as electrolyte.

2008-03-25 23:48:22 補充：
Although the presence of low reactive metal ions may cause displacement reaction,
it is not the main reason why sea water speed up rusting.

2008-03-25 23:48:32 補充：
1. The conc. of those ions are low.
2. Fe + CuCl2 → FeCl2 + Cu
The above reaction does not involve the action of oxygen.
i.e. the transfer of e- from Fe to oxygen.

high temp=chemical reaction 快左
(個example就好似你放d食物去雪櫃冇咁易壞..其實除左rusting外好多野係high temp. 佢既reaction都會快d)
有海水=有salt
(salt係1個ionic bond做既野...dissolve係水就有mobile ions 會增加水既導電性 .. 咁就會令到iron易d lose electron 成為 iron(iii) <---rusting 既物質)