chemical equations!

[ltee]

what are the chemical equations we need to know?
ive been seeing clashing ones and its really confusing me

can someone tell me what the hydrogen-oxygen fuel cell equations and the lead acid battery are?

thanks in advance!

[cara.mel]

The fuel cell half equations are on the electrochemical series. You just have to be careful whether you're in an acid or alkaline cell

Lead-acid battery:
Anode Pb + SO4 2- -> PbSO4 + 2e-
Cathode PbO2 +4H+ + SO4 2- +4e- -> PbSO4 + 2H2O
Overall: Pb + PbO2 + 2H2SO4 + 2H+ -> 2PbSO4 + 2H2O
You do not need to know these, they will give you at least the half equations, or the full equation and make you derive the other one etc. But because they show up so often, it's nice to know them.

From food chem need to know photosynthesis/respiration, think they're the only specific ones

Also it is a good idea to know equations involving Na2O, Al2O3, SO3
Na2O with an acid: Na2O + 2HCl -> 2NaCl +2H2O
Na2O with water: Na2O + H2O -> 2NaOH
Al2O3 with an acid: Al2O3 + 6HCl -> 2AlCl3 + 3H2O
Al2O3 with base: Al2O3 + 2OH- + 3H2O -> 2Al(OH)4 -
SO3 with base: SO3 + 2NaOH -> Na2SO4 + H2O
SO3 with water: SO3 + H2O -> H2SO4
(don't need to be those exact ones, just need to be able to write an equation if asked for it)

Oh and also from this AoS, the reaction in the sun is 4H -> He + 2e+

Chances are I've probably forgotten something

[ltee]

OMG I COULD BLOODY HUG YOU!
thanks so much cara.mel      
i almost forgot about the oxide reactions !

youre so going to nail the exam haha

[principe]

Half reactions for the Hall-Heroult Cell are also very common. But as cara.mel said they usually give you one half equation and/or the overall equation that you can use to derive the other half equation. So I would either study how to derive cathode/anode reactions from an overall equation or memorize the equations, which isn't complicated. I suggest the former because that way you get a better understanding about writing half equations. But if you feel that you don't have enough time to learn how to write half equations, since the exam is in two days, it would be good to memorize them.

Cathode:
Al3+(cryolite) + 3e- -> Al(l)

Anode:
C(s) + 2O2-(cryolite) -> CO2(g) +4e-

Overall:
2Al2O3(cryolite) + 3C(s) -> 4Al(l) + 3CO2(g)

Sorry I don't know how to do subscript and superscript

[Collin Li]

what are the chemical equations we need to know?
ive been seeing clashing ones and its really confusing me

can someone tell me what the hydrogen-oxygen fuel cell equations and the lead acid battery are?

thanks in advance!

Don't need to know either, IMO.

Some people would say you need to know lead-acid, but I doubt that. In 2006, there was the hydrogen-oxygen fuel cell, but there was enough information (telling you the reactants and products) to derive the half equations from first principles.

You should look at whether or not the fuel cell is alkaline or acidic, that usually gives away something about the presence of H+ or OH-.

Something cara.mel didn't mention was the electrolytic industrial processes (all three), otherwise, great job.