noob chem questions

[azario]

during electrolysis 78000 electrons were pumped into the cathode. determine the mass of the product deposited.

2 half equations are :
Fe2+ + 2e=Fe

Cu2+ + 2e= Cu


question2:
6O2 + C6H12O6= 6H2O +6CO2
is this exothermic or endothermic
answers say it is endothermic  but isn't it reverse of photosynthesis so therefore it should be exothermic.

[b^3]

First question.
We know the number of electrons. So we need to work out the amount in mol of electrons.
So N=n*6.02*10²³
n=78000/(6.02*10²³)
=1.296*10^-19 mol

Now we need to know what metal will be deposited at the cathode. This will be the one that is undergoing reduction (gaining e^-), so it is the strongest oxidant and is highest up on the left side of the electrochemical series. That is Cu²⁺
so we know we have the equation at the cathode to be
Cu²⁺(aq)+2e^--->Cu(s)
So using mol ratios, 2 mols of e^- will deposite 1 mol of Cu.
So n(Cu)=n(e^-)/2=6.478*10^-20mol
m(Cu)=n(Cu)*m(Cu)
=6.478*10^-20*63.55
=4.117*10^-18g

Hopefully there are no mistakes in there.

Second Question.
Respiration is exothermic so it may be a mistake or there may be a different interpreation of the question.