Rusting - Can some one explain?

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[Announcements] [Introduce Yourself] [ICT] [Prasekolah] [LINUS] [KSSR] [UPSR] [PMR] [SPM] [STPM] [School] [Classroom] [Clubs & Uniformed Bodies] [JPN] [SPA] [SICT] [SPP] [SPS] [SPPK] [SPSPK] [SPI] [SPsK] [JNJK] [PPD] [Program] [Computer & Internet] [Let's Hear It From You] [Membergroup]

[Wong Hee Ting]

The effect of other metals on the rusting of iron:

If iron is contact with a metal that is less electropositive, iron will be oxidised to iron (II) ion, then it will combined with hydroxide ion from water, caused a little pink colouration.

If iron is contact with a metal that is more electropositive(eg, Zn), zinc will be oxidised to zinc ion. Why zinc ion will not combine with hydroxide ion from water? Because the intensity of pink colour is very high.

Can some one explain?

[Patrick Chai Teck Khiong]

Student had asked me before bout this ques.  I'm told them this is rusting process and only iron(II) ion will react with hydroxide ion to form rust. and don't think further.. That's what i said to my student..How about the others??

[Jong Kah Yin]

Hi,
Will try to offer my opinion here.

For metals like Zn / Mg paired with Fe, the pink colour intensity is high - because Zn & Mg is much more electropositive and will release electrons easily. The water & oxygen will accept electrons to form hydroxide ions which turns phenolphthalein pink

If iron is paired with less electropositive metals , iron will be oxidised but iron is less electropositive than Zn / Mg, therefore the electrons released will be much less and in turn produces less hydroxide ions, thus giving lower intensity of pink colour.

[Wong Hee Ting]

Thanks for the explaination

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