q63 topscore 2

[queenskillers]

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in the chemistry section of the test, this question asks, how many faradays are required for the reduction of 2 moles of Fe 3+ to Fe(s)> The answer is 6 F since there are 6 moles of electrons. How the hec does this make sense since if you multiply number of electrons by the faradays constant (coloumbs/moles of electrons) the answer would be in coloumbs/ please help

 

[denticus]

That's right, but the question specifically asks for Faradays. Since iron is +3 then 3 electrons are needed per iron molecule to reduce is to Fe(s) times 2 moles of iron will equate to 6 moles of electrons needed or 6 Faradays. You could rephrase the question by asking how many Coulombs are needed to reduce the 2 moles of Fe+3 at which point you would take your previous answer, 6, and multiply that by how many Coulombs there are in each Faraday (96,800 coulombs/faraday) and then you'd be left with coulombs. But it doesn't ask for coulombs it asks for Faradays so your answer is the first, or 6 faradays.