F.4 Chem plz help 20點!!!

Actually, I don't know what the chemical equation of the reaction is. And I am not really sure my answer is exactly correct. But I hope I can answer your question.

The aluminium oxide layer will react with the hydrogen ions in the hydrochloric acid to form aluminium ions and water.

When the oxide layer is gone, the mercury(II) chloride solution is reacted with the aluminium quickly. The aluminium is then covered by a thin layer of amalgam. This amalgamted layer can be dissolved in the water just formed from reacting the aluminium oxide and hydrochloric acid.

most likely mercury(II) chloride is not a catalyst.
#1 answer is reasonable: mercury reacting with unprotected aluminium to form an amalgum (mercury alloy); aluminium in amalgum reacts with water to form aluminium hydroxide, which is suspended in water and does not cover the Al surface.

2013-12-28 13:26:19 補充：
Correction: amalgam
all 3 vowels are A

Aluminium Oxide layer first removed by dilute hydrochloride acid
Al2O3 + 6 HCl ->2 AlCl3 + 3 H2O
Aluminium Chloride dissolves in water to give out aluminium ions

Since the reaction takes place for long, the presence of mercury (ii) chloride
is used like a catalyst.