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Name: Sean
Status: student
Grade: 12+
Location: Outside U.S.
Country: Australia
Date: April 7, 2011


Question:
As part of my school course, I have been given 3 random 'silvery' metals from a particular set and asked to identify them. I have been doing chemical and physical tests and I have been receiving very odd results for one of these metals. I have tested its density, and it appears to be Aluminium. When I have tried to verify this chemically, I have received some very obscure results. The supposed 'Aluminium' has no reaction with Hydrochloric Acid (6M), contrary to what the reactivity series tells me. Secondly, when I tried to create a reactivity list for the metal by testing it with nitrates/chlorides of the different possible metals, I received some odd results. The metal did not react with silver nitrate or any of the other nitrates/chlorides except for the Tin Chloride. This results have left me completely baffled and I do not know what to do. I have heard of the oxidation process of aluminium, but I am having great difficulty in researching how it should react.



Replies:
Start with a chart of the periodic table. "X" out the obvious non-metals, e.g. F2, Cl2, O2 etc. "X" out the unlikely elements, even metals, the rare earth metals, Lanthinum etc., Uranium, etc. "X" out the highly reactive hazardous metals such as Na, K, Rb, Cs etc. "Y" out unlikely metalloid candidates such as Bi.

Now you have a reasonably few metallic elements remaining so that you can start doing some chemical testing. This also means you may have to look up some properties of metals. I will give you one hint, but the others are yours to test and eliminate and/or confirm. Aluminum, among the remaining metals, passes the tests above, plus it reacts with strong bases (pH > 10) evolving hydrogen gas.

Keep doing this for the remaining elements -- both the physical and chemical properties. You will find that the remaining metals that pass the tests above are few.

Chemical identification is frequently a process of elimination. This is your exposure to that procedure, which is the purpose of the experiment.

Good Searching (not good luck). You don't need luck.

Vince Calder



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