chem about rusting

2010-06-08 3:13 am

iron nail wrapped with a copper wire,用indicator test,
iron nail既頭同尾blue(有rust),中間係pink(有hydroxide ions)

1)why中間唔係blue?(冇rust?),係咪放耐d會有??
2)iron nail既頭同尾係咪唔會pink?(冇hydroxide ions?)

iron nail wrapped with a magnesium ribbon,用indicator test,
iron nail既頭同尾pink(有hydroxide ions)

3)why中間唔係pink?(中間冇hydroxide ions?)

help me please><

更新1:

sorry...我想問返第2個situation magnesium ribbon wrap在iron nail中間 O2同Mg react but why iron nail既頭同尾會有hydroxide ions? iron nail唔係冇react過咩??

回答 (1)

[匿名]

2010-06-11 8:39 pm

✔ 最佳答案

What are included in your solution?
The rusting indicator should contain potassium hexacyanoferrate 3 solution,NaCl(aq) and phenolphthalein.

1)If iron nail wrapped with a copper wire, blue colour should appear,since iron is higher in e.c.s than copper, then iron lose electrons more steadily,then iron will lose electrons to form iron 2+,the Fe2+ react with potassium hexacyanoferrate 3 solution to form blue complex.

2)Aroung copper,O2 and H2O get the electrons to form the OH- which turn phenolphthalein pink.

3)Mg-->Mg2+
electrons move to iron and form OH- with O2 and H2O,therefore there is no FE 2+ iron , so there is no blue complex.In the middle , there is only Mg2+ ions,the hydroxide ions are move to the iron.

參考: By my knowledge

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