為什麼氧化鋁不能用碳還原法?

鋁是很活潑的金屬，它的活潑性僅在鎂之下而在鋅之上。

金屬愈活潑，其氧化物愈穩定。由於鋁是很活潑的金屬，故此氧化鋁非常穩定。要把氧化鋁還原為鋁，碳的還原能力明顯不足，因此不能用與碳共熱的方法把氧化鋁還原為鋁。

碳的還原能力，只可以還原氧化鋅，以及還原活潑性較鋅低的氧化物。由於鋁較鋅活潑，故此不能用與碳共熱的方法去還原氧化鋁。

還原氧化鋁的方法通常是把溶融的氧化鋁電解。

2014-04-25 20:29:42 補充：
把氧化鋁與碳共熱，碳在空氣中燃燒而氧化鋁沒有反應。只是浪費了碳，以及製造室溫氣體二氧化碳而已。

To Hin :

Decomposition of a chemical change.

How can you use physical method to make a chemical change (decomposition) occur ? It is ridiculous !

Potassium Sodium Calcium Magnesium Aluminium
If you want to extract those metals from its ores 礦石

Because many metals are too reactive, so they combine with oxides carbonates or sulphides as compound , called ores

Aluminium is a very reactive metal so its compound is very stable
It is very difficult to reduce the Al metal by using the carbon reduction.
Therefore , it must be extracted by using electrolysis , a very power extraction
method

If a metal is reactive, its compound is very stable
I f the metal is very unreactive like Au and Pt ,its compound is very unstable ,
so we can simply decompose the compound by heating or even physical method.

2014-04-22 14:50:28 補充：
we always decompose **motlen**Aluminium oxide by electrolysis . But not the aqueous solution of the aluminium oxide

因為要拆開佢地之間既bond需要用好多energy...唔係唔得而係唔實用