Q5A from 2009 TSSM Chemistry Unit 4

[Grey]

Hey guys can anyone help me with getting the equations from the TSSM 2009 Trial Exam, because what i got was:

Anode: 2Li + S^- >>>>> Li₂S + e^-        (-) electrode
Cathode: 2e^- + FeS₂ >>>>> Fe + 2S^-              (+) electrode

I mean I checked the answers and they didn't even have the sulfur atom in the half-equations....thats kinda weird because it creates the question, where does sulfur come from within the overall equation?

Thanks.

[simpak]

I got the same equations as you!  DDDDDDD:

[Grey]

haha im pretty ready for chem u reckon tssm 09 was pretty hard? i reckon it was challenging.

[simpak]

I just did it about two hours ago, and I thought it was alright.  I didn't find it too bad, but it was very short!
I usually have heaps of trouble finishing in time, but I finished like 20 minutes early.

[TheJosh]

i think its a molten cell so the Sulfur and lithium are just ions and so in the half equation thats why you dont include sulfur in half

equations
 

[Grey]

yeah yeah it was short but only got 84% for it >< finished 20mins early i mean i understand every detail on this stuff but u know your stuff and u write these equations which add up to the overall, but it just doesnt work its just wrong!?

[Grey]

oh so they're just spectator ions? if i include them does that mean im wrong? =S

[TheJosh]

they probably are spectator ions

I think if you added them in equation as ions they would cancel anyway?

[Grey]

no no it doesnt work >< someone please help!!

[simpak]

Ummmm I put...
2Li + 2S- ---> Li2S + 2e-

FeS2 + 2e- ----> Fe + 2S-

And when you add them, it turns into the real equation.
I don't see how that's wrong at all...
Maybe it is okay to keep the S's.

[simpak]

Waiiiit a second, I just reread that.
...That's odd.  It doesn't cancel, the first equation is wrong.

[Grey]

SORRY GUYS
i know my mistake now, if you're having trouble guess what?
the sulfur ion is a negative 2 charge not negative 1 which means that the sulfur ion is just a spectator ion and can be omitted from the main equation, thats all guys thanks for your help [=[=[=[=[=[=

[simpak]

Alright, man, I hope that doesn't come up tomorrow though, I'm bound to confuse myself.

[TheJosh]

SORRY GUYS
i know my mistake now, if you're having trouble guess what?
the sulfur ion is a negative 2 charge not negative 1 which means that the sulfur ion is just a spectator ion and can be omitted from the main equation, thats all guys thanks for your help [=[=[=[=[=[=

wat i was tryn to say ^^

[ScyLLa]

if sulfur is an -2 charge, then how does FeS2 exist?? isnt Fe 2+ charge, and if sulfur is a -2 charge, they cancel out and therefore should be FeS??

i didnt recognise the Fe (4+)

sorry guyz