oxidation and reduction

2006-12-29 12:48 am
我有d野唔明@@
唔該幫我解釋下列句子。
1) It bleaches by oxidation.
2) It bleaches by reduction.
3) Sulphur dioxide is oxidized to sulphate.
4) It oxidize iodide ions to iodine molecules.
5) It is reduced.
6) It is oxidised.
其實上面只係1d例子。
我最想問的是幾時用is oxidised; it oxidize...; is reduced ; it can be reduced...?
10分感謝!

回答 (2)

2006-12-29 2:42 am
✔ 最佳答案
Reduction is a process that a substance gains electrons.
Oxidizing agents is a substance that gains electrons.
Therefore, oxidizing agents ALWAYS undergo reduction. They are reduced.

Oxidation is a process that a substance loses electrons.
Reducing agent is a substance that loses electrons.
Similarly, reducing agents ALWAYS undergo oxidation. They are oxidized.

You should first find out whether a substance is a reducing agent or an oxidizing agent(Just memorizes those in your textbook). Then you will know whether it undergoes reduction or oxidation.

For example,
acidified potassium permanganate is an oxidizing agent.
Thus it ALWAYS undergoes reduction and being reduced.
2006-12-29 3:06 am
(1)和(2)所說是漂白過程中,如用上的漂白化學物不同,便有不同的漂白作用。
簡單來說,含有氯化物例如氯酸鹽 (ClO) - 負離子的化學物,其漂白過程是透過氧化作用 (oxidation),因為當中的氯 (Cl) 的氧化數 (oxidation number) 由 +1 變成 氯氣 (Cl2)裡的 0
而用二氧化硫 (SO2)來漂白,其漂白過程是透過還原作用 (reduction),因為當中的硫 (S) 的氧化數由 +4 變成硫化鹽 (SO4)裡的 +6
所以(3)裡面所說的二氧化硫被「氧化」(oxidized) 為硫化鹽,就是因為當中硫的氧化數,有著上述的變化 (增加)。
在(4)裡面,並無指定是何種東西將碘離子(I -)「氧化」為碘份子 (I2),但由於在這個過程中,碘的氧化數由 -1 增加成 0 (元素的氧化數永遠是 0) ,即是說,碘是「被氧化」。
(5)和(6),總言而之,凡是某東西A在化學過程中,其氧化數增大的話,A就是被氧化 (A is oxidised) ,而相對地有一個物質B在化學過程中,其氧化數減少了的話,B就是被還原 (B is reduced),而B就相對地氧化了化學過程中的物質 (B oxidises ...)


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