Homework Help: chemistry

Posted by harish on Sunday, March 10, 2013 at 6:39am.

Plastic articles can be chromium-plated by coating them with thin layer of graphite paste,placing them in a bath of aqueous chromium(III) sulphate and electroplating.
a)Suggest a reason why the article is first coated with graphite.
b)what substance could be used for the other electrode in the electroplating cell/
c)Draw a diagram of the electrical circuit for the electroplating.
d)If a current of 0.5 A were passed through the cell for 300 sec,what would be the increase in mass due to the chromium plating?
e)why is it not possible to coat articles with zinc by this method?

chemistry - DrBob222, Sunday, March 10, 2013 at 2:49pm
The plastic article must be one of the electrodes but it doesn't conduct electricity. Therefore, the graphite coasting serves that purpose.

I would think a graphite rod or carbon rod would serve as the other electrode.

amp x seconds = coulombs
0.5A x 300 s = 150 coulombs,
96,485 coulombs will deposit 52.0/3 = 17.33 g Cr.
g Cr plated = 17.33 x 150/96,485 = ? g Cr.

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