electrochemistry question

[yingao]

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I have no idea how to do this question. CAn someone help me please?

to give "white gold" a white appearance. it is plated with rhodium that wears away with time and must be replaced using immersion in a rhodium sulfate solution (Rh2(SO4)3aq). Provide with a current of 2.0 A, how long must a 3.0g white gold broach be immersed to plate 30 x 10^-6g of rhodium ( Faraday=96500C/s)

1. ----0.0009s
2.----0.0098s
3.----0.042s
4.----0.56s

 

[IntelInside]

I have no idea how to do this question. CAn someone help me please?

to give "white gold" a white appearance. it is plated with rhodium that wears away with time and must be replaced using immersion in a rhodium sulfate solution (Rh2(SO4)3aq). Provide with a current of 2.0 A, how long must a 3.0g white gold broach be immersed to plate 30 x 10^-6g of rhodium ( Faraday=96500C/s)

1. ----0.0009s
2.----0.0098s
3.----0.042s
4.----0.56s

Rh+3 + 3e --> Rh (s)

moles of electrons transferred = 3 x [(30x10^-6)/103] = 9 x 10^-7 mol e

96500 C/mol e x (9 x 10^-7 mol e) = .086 C

.086 C / 2 C/s = .043 s

 

[yingao]

Thanks a lot!!

 

[kpatel26]

Thanks a lot!!

Why do you use moles of rhodium instead of gold? Instead of 3 g why do you use the 30 x 10-6g?