[wk1234]

I have tried to do the following question but i cannot seem to work it out.

2 ZbO(s) + ½ O₂(g) -> Zb₂O₃(s)            –128.0 kJ
ZbO(s) + ½ O₂(g)  -> ZbO₂(s)                –380.0 kJ
2 ZbO(s) + 3/2 O₂(g)  -> Zb₂O₅(s)          –344.5 kJ

find the value for:
Zb₂O₃(s) + O₂(g)  ->  Zb₂O₅(s)    = enthalpy for this?

I have tried using hess's law but i cannot seem to find the enthalpy for the last equation. I know flipping first  equation gives you the Zb₂O₃(s) on the left side and cancels a lot of it out but i dont know how to solve it from there. (it cancels out ½ O₂(g) and two ZbO(s) from both sides yet still leaving one on the left which i dont know what to do with)

[nj_bartel]

Try multiplying everything by 2 to get rid of the decimal, see if that makes it any clearer.

[wk1234]

thx for replying. It doesn't help much by multiplying b/c i only get double of what i cant seem to get rid of.

I got Zb₂O₃(s) and  Zb₂O₅(s) in this right spots but i also have:

- ZbO₂ which has no counter part to get rid of it. (on right)
- 3/2 O₂ (left)
- ZbO(s) (left)

Any way to cancel them that i dont know about? Like can you split ZbO₂ apart and get rid of O in that to cancel out the other one? Thx for is greatly appreciated.

[stmoney]

I'm also curious as to what to do with that ZbO2(s)... is this problem from a book or one your teacher gave to you? Maybe there was a typo?

[wk1234]

Ya thats the one i was wondering about. There is no typo in here and i cannot seem to  get rid of that one! I got rid of almost everything else.

Its an online hw problem.

[enahs]

Of the three reactions with enthalpies you have, you only need the first and last one. A quick glance and I do not think you even have to do any stoichiometry either.

[macman104]

Of the three reactions with enthalpies you have, you only need the first and last one. A quick glance and I do not think you even have to do any stoichiometry either.

Nope, no stoichiometry.  Ignore the middle equation.

EDIT:  Stoichiometry, not stereochemistry, lol

[enahs]

Aww come on, I was trying to leave them something to think about even if it is obvious to others!

[wk1234]

Ah ok lol. I had a weird idea i needed all of them

Well thx for the tip!!

[macman104]

Aww come on, I was trying to leave them something to think about even if it is obvious to others!

  What more did I reveal?