[1z3]

When doing past papers, I often lose marks in the equation balancing department. I've looked online/youtube to find a reliable way of balancing any equation and I'm always left disappointed.

The only reliable method I seem to know is simply trial and error but this often lets me down as reactions become more complicated.

For example, I've been trying for around 20-30mins now trying to balance the half cell reactions in a direct alkaline ethanol fuel cell:
I've worked out the oxidation and reduction reactions but I am stumped on how to balance them using a reliable logical process. I can look up the answer but I need to know how for the exam.

C2H5OH + OH- ----> CO2 + H2O + e-
O2 + H2O + e- -----> OH-
I know the overall is simply combustion of ethanol: C2H5OH + 3O2 ----> 2CO2 + 3H2O

If anyone could help, it would be greatly appreciated.

[mikasaur]

http://chemwiki.ucdavis.edu/Core/Analytical_Chemistry/Electrochemistry/Redox_Chemistry/Balancing_Redox_reactions#Basic_Conditions

Be very careful about multiplication and addition and writing clearly. It's easy to mess up one little thing and then the whole process is thrown out of whack.