A fuel cell designed to react grain alcohol with oxygen has the following net re
ID: 984512 • Letter: A
Question
A fuel cell designed to react grain alcohol with oxygen has the following net reaction: CH3OH(l) + 3/2 O2(g) --> CO2(g) + 2H2O(l) The maximum work one mole of alcohol can yield by this process is 703 kJ. What is the theoretical maximum voltage this cell can achieve?
Heres the answer
The given reaction is an example of the redox reaction:
CH3OH (l) + 3/2 O2 (g) --> CO2 (g) + 2H2O
In this reaction the oxidation number of carbon change from -2 to +4 by loses of 6 electrons.
Given that; "The maximum work one mole of alcohol can yield by this process is 703 kJ",
means the dG for this reaction = -703kJ or -703000 J
using "F", faraday's constant:
dG = - nFE
Here; n = 6 electrons and, F =96500 J / mol e-volt
-703000 J = - (6 mol e-) (96500 J / mol e-volt) E
E = 703000 J / (6 mol e-) (96500 J / mol e-volt)
E = 1.21 volt
My questions is, why does work or dG become negative (-703kJ)?
Explanation / Answer
CH3OH (l) + 3/2 O2 (g) --> CO2 (g) + 2H2O
dG negative of a reaction indicates that its a spontaneous reaction and moreover the given reaction is a redox reaction.