CE Chemistry

1.
In the absence of water (when dry), cobalt(II) ion is blue (藍色)。
In the presence of water (when wet), cobalt(II) ion is pink (粉紅色)。

2.
Halide means:
(1) the anion of a halogen, i.e. F-, Cl-, Br- and I.
(2) a halogen-containing compound, e.g. CH3­Cl.

3.
K, Na, Ca, Mg, Al, Zn: They are extracted by electrolysis of the molten oxides (e.g. Al2O3) or chlorides (e.g. NaCl).

Fe, Pb, Cu: They are extracted by heating the ores with carbon.

Hg, Ag: They are extracted by heating the ores in air.

Pt, Au: It is not necessary to extract chemically because they exists as elements in nature. Only physical methods (e.g. remove the dust on the surface) are needed.

4.
K, Na and Ca can undergo displacement reaction in molten state. For example, in liquid state, sodium can displace zinc (in the absence of air to prevent oxidation).
2Na(l) + Zn2+(l) → 2Na+(l) + Zn(l)

In the presence of water, K, Na and Ca would react with water, but would not undergo displacement.

5.
The particles of the Al2O3 are packed very tightly, and thus the layer does not allowed the atmospheric oxygen to pass through. This prevents further corrosion.

The particles of the oxides of the other metals are not packed tightly, and thus the layers allow the atmospheric oxygen to pass through. This allowed further corrosion to occur. Furthermore, the oxide of the most other metals would catalyze the further formation of the oxide.
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2009-04-30 01:10:34 補充：
Q.3

The first group should be "K, Na, Ca, Mg, Al"

The second group should be "Zn, Fe, Pb, Cu"

上面個答案有少少錯ga...

第3題: Zn 應該係用carbon reduction黎extract的
即係同Fe,Pb,同埋Cu ge method一樣