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bond enthalpies

Help on question 2 pls

@EricPiphany @samb1234
2.1 Exercise 2 - Bond dissocation enthalpies.doc34.3KB
Original post by thefatone
Help on question 2 pls

@EricPiphany @samb1234


12N2(g)+32H2(g)→NH3(g)\frac{1}{2}N_2(g)+\frac{3}{2}H_2(g) \rightarrow NH_3(g)

You know ΔHb of H2\boxed{\Delta H_b \ \text{of }H_2}, ΔHb of  N2\boxed{\Delta H_b \ \text{of } \ N_2} and ΔHf for NH3\boxed{\Delta H_f \ \text{for } NH_3}
(edited 8 years ago)
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thefatone
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Original post by Kvothe the arcane
12N2(g)+32H2(g)⇒NH3(g)\frac{1}{2}N_2(g)+\frac{3}{2}H_2(g) \Rightarrow NH_3(g)


multiple don't make a difference right? so i put a 3 in from of the H2 and a 2 in from of the ammonia

so what did you work out the average bond enthalpy as?
Original post by thefatone
Help on question 2 pls

@EricPiphany @samb1234


WP_20160314_14_49_36_Pro.jpgSpoiler
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thefatone
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Original post by EricPiphany
WP_20160314_14_49_36_Pro.jpgSpoiler


sure? the answers tell me +390.8 kJmol-1 but i get the same answer as you.....
Original post by thefatone
sure? the answers tell me +390.8 kJmol-1 but i get the same answer as you.....


I get 390.83 kJmol−1390.83 \ kJmol^{-1}

Your mistake is that enthalpy change of formation is when one mole of the product is formed.
(edited 8 years ago)
Original post by Kvothe the arcane
I get 390.83

Your mistake is that enthalpy change of formation is when one mole of the product is formed.

You're correct.
Original post by thefatone
multiple don't make a difference right? so i put a 3 in from of the H2 and a 2 in from of the ammonia

so what did you work out the average bond enthalpy as?


No. But then you would have to multiply −46-46 by 2 as 2 moles of NH3 are being formed. Your answer isn't that far off as you're dealing with large quantities and 46 is small in comparison.
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Original post by Kvothe the arcane
No. But then you would have to multiply −46-46 by 2 as 2 moles of NH3 are being formed. Your answer isn't that far off as you're dealing with large quantities and 46 is small in comparison.



ah right i forgot thanks a ton guys

Original post by EricPiphany
You're correct.
I guess I'm too late

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