the enthalpy change of formation for N2O?

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roshni_khanna
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So far, I've been given the equation:
N2 + 0.502 -----> N20

And I've been told the enthalpy change of formation for the following reactions:

C + N2O -----> CO + N2 = -193

C + O.5O2 -------> CO = -111

Now from that information I'm required to work out the enthalpy change of formation for N2O. any ideas how do do this? Am i meant to draw a Hess's cycle? I'm so stuck!!!

Thanks in advance guys!

Oh, and by the way the answer is +82
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Tappouni
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(Original post by roshni_khanna)
So far, I've been given the equation:
N2 + 0.502 -----> N20

And I've been told the enthalpy change of formation for the following reactions:

C + N2O -----> CO + N2 = -193

C + O.5O2 -------> CO = -111

Now from that information I'm required to work out the enthalpy change of formation for N2O. any ideas how do do this? Am i meant to draw a Hess's cycle? I'm so stuck!!!

Thanks in advance guys!

Oh, and by the way the answer is +82
Yes you'll have to draw a Hess's cycle for that In your overall equation, N2O is the product, and N2O is present in one of those cycles...but it's a reactant rather than a product, so that reaction effectively goes in a the opposite direction, so you have to reverse the sign to +193.

If you've switched that around, one of the reactant molecules for that second stage then becomes CO, but as the second of those equations is already showing the formation of CO, you'd leave the sign that way around.

So -111 + (+193) = +82 which is the enthalpy change of formation...if that doesn't make sense I'll draw the Hess diagram
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roshni_khanna
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(Original post by Tappouni)
Yes you'll have to draw a Hess's cycle for that In your overall equation, N2O is the product, and N2O is present in one of those cycles...but it's a reactant rather than a product, so that reaction effectively goes in a the opposite direction, so you have to reverse the sign to +193.

If you've switched that around, one of the reactant molecules for that second stage then becomes CO, but as the second of those equations is already showing the formation of CO, you'd leave the sign that way around.

So -111 + (+193) = +82 which is the enthalpy change of formation...if that doesn't make sense I'll draw the Hess diagram
Yes please, I'm sorry could you draw one please Chemistry really isn't my strong point! I don't see how the second equation relates to the formation of N2O at all...
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Tappouni
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(Original post by roshni_khanna)
Yes please, I'm sorry could you draw one please Chemistry really isn't my strong point! I don't see how the second equation relates to the formation of N2O at all...
See if this makes any more sense? It's a tricky one to explain
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roshni_khanna
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(Original post by Tappouni)
See if this makes any more sense? It's a tricky one to explain
OK thanks I understand it a bit better now! But for 1 oh Hess's cycle I don't understand how the enthalpy is the same even when there's the extra nitrogen's in the equation
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Tappouni
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(Original post by roshni_khanna)
OK thanks I understand it a bit better now! But for 1 oh Hess's cycle I don't understand how the enthalpy is the same even when there's the extra nitrogen's in the equation
There's the right number of nitrogens, but you'll have to ignore the carbons, because technically the overall equation should be N2 + 1/2O2 ----> N2O + C

Bit of a misleading question
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Borek
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There is no extra carbon, there is no extra nitrogen.
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Tappouni
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(Original post by Borek)
There is no extra carbon, there is no extra nitrogen.
Surely the overall equation should include the carbons though?
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Borek
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Not sure what you mean by overall equation - you are asked about the reaction of the nitrogen oxidation, and you have to express it using two given equations. If done correctly, there will be no carbon nor nitrogen left, you will be left just with the original equation.

-first:

N2 + CO = C + N2O

+second:

C + 1/2O2 = CO

-first+second:

N2 + 1/2O2 = N2O
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roshni_khanna
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(Original post by Tappouni)
There's the right number of nitrogens, but you'll have to ignore the carbons, because technically the overall equation should be N2 + 1/2O2 ----> N2O + C

Bit of a misleading question
well thanks for your help
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Tappouni
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(Original post by roshni_khanna)
well thanks for your help
No worries
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smallshotz
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(Original post by Tappouni)
No worries
lol i know im 5 years late but that helped now looool hows uni going ?

IF you're even alive........................... .......
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