rusting(best ans:awarded 40pts)

Rust can be removed by AN ACID because rust is usually metal oxides. Neutralization occurs: acid + metal oxide (base) --> salt and water.

So rust can be removed by acidic solution

However, when immersed in an acidic solution, as acid is an ELECTROLYTE, iron loses electrons MORE READILY to produce iron (II) ions. So it rusts more readily.



So both 1 and 2 are correct.

However, the MAIN DIFFERENCE is

1. The acidic solution is rubbed against the rust slightly. For example, use a towel to dip a bit of acid on the rust. Neutralization occurs. The contact time and surface is small.

2. The iron should be TOTALLY IMMERSED in an acidic solution for a long time for rust to occur.

So TIME and AREA OF CONTACT are factors that affect whether the iron in contact of an acid will rust.

希望我可以幫到你！！

2007-01-14 12:07:29 補充：
P.S. Hope you don't mind my bad English.

2007-01-14 12:34:05 補充：
P.P.S. For 1, a very common application is:Metal woks鍋 usually have brown stains when in use for a long time. Those are metal oxides, formed when the metal is exposed to air. To remove them, use lemon juice containing citric acid. Neutralization occurs.

2007-01-14 12:34:13 補充：
Note the lemon juice is only in contact of the wok for a SHORT PERIOD OF TIME, and small amount of juice is used. So the rust is REMOVED instead of WORSENED (it will worsen when it is immersed in an acidic solution)

第一句無錯...rust on iron係Fe3O4，而當acid 加上呢度時會有neutralization...的確係可以remove rust的...

第二句都無錯，因為Fe可以同acid react，咁就會出Fe3O4...呢D就係rust...

咁點解呢？

首先有樣野要明白，一粒iron nail放入acid入面，Fe會先同acid react form Fe3O4，因為一粒鐵釘只係得iron，無Fe3O4...而form出來的Fe3O4，才會同acid做neutralization...所以個過程會係咁：(我地先假設acid係HCl)

Fe ----HCl--->Fe3O4---HCl---->FeCl3

FeCl3溶左落水...的確照度理咁看，的確會remove rust...只係粒釘會越來越短...不過，從實驗我們知道不是如此...

這是因為reaction rate的問題，前面reaction個rate比後面reaction個rate係快好多好多...所以，iron唔會remove rust...