Electrochemistry question

[annospree]

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The gold-plating process involves the following rxn: Au+3 +3e- --->Au(s). If this is done for 35 min. with a 7 A current, how many grams of Au will be plated?

I got 10.0 g, but Kaplan says it's 9.85 g and I think they're wrong!

 

[BerkReviewTeach]

The gold-plating process involves the following rxn: Au+3 +3e- --->Au(s). If this is done for 35 min. with a 7 A current, how many grams of Au will be plated?

I got 10.0 g, but Kaplan says it's 9.85 g and I think they're wrong!

Did you multiply 35 min x 60 sec/min x 7 C/sec and then divide by 96,500 C/mole e- to get the total number of electrons? That number is then divided by 3 to get the moles of Au formed. Finally, you multiply by 197 g/mol. That works out to be 10g by my math.

If 9.85 is the closest answer choice, then that's what you need to pick. Maybe it's not an error but they've intentionally put all four numbers as incorrect to teach you to look for the best answer rather than the correct answer.