chemistry
posted by hriday .
the quantity of electricity required to reduce 12.3g of nitrobenzene to aniline assuming 50% current efficiency is
1. 115800 C
2. 57900 C
3. 231600 C
4. 28950 C

You multiply 12.3 by .50 to get 6.15 so none of those are the answer. simple!

Check my thinking on this.
C6H5NO2 ==> C6H5NH2
molar mass C6H5NO2 = 123
Change of electrons is 6, N going from +5 oxidation state to 1 oxidation state or gain of 6 electrons.
Therefore, 1 Faraday or 96,485 coulombs will reduce 123/6 = 20.5 g C6H5NO2. But since the efficiency is only 50%, it will reduce only half that amount or 20.5/2 = 10.25 g or 10.25/123 = 0.08333 mole.
How many moles do we have? That is 12.3/123 = 0.1; therefore,
# coulombs = 96,485 C x (0.1/0.08333)= ??
Check my work. 
57900

Change in o.s=6
Now 6 F is req'd to reduce 1 mole
Therefore for 12.3/123=0.1 mole we need
0.1*6=0.6 F
But since current is 50℅ efficient..
Therefore for 0.6 we need 0.6*2=1.2 F
1.2*96500=115800 C