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OCR AS - Chemistry Unit F322 - Chains, energy and resource - REVISION!

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for the shape I got the first one as tetrahedral but forgot the second one, guessed pyramidal, guess thats wrong ;L
Reply 741
Original post by EternalDoom
Hmmmmmmmmmmms, what did people put for why enthalpy change of formation was hard to calculate exactly? I said it was hard to perform under standard conditions


Only questions that were hard were the little 2-markers that havent come up in past papers


I put that other compounds might've been formed by the reactants. :dontknow:
Original post by EternalDoom
Hmmmmmmmmmmms, what did people put for why enthalpy change of formation was hard to calculate exactly? I said it was hard to perform under standard conditions


Only questions that were hard were the little 2-markers that havent come up in past papers


Other products produced, slow rate, high activation energy, is what I put, as it didn't specify that it wanted only one answer, which they usually do with, "Give one reason why etc..."
Anyone get plus 1279?
Original post by Abused Tampon
what did people get for the question about the enthalpy change of amonia? N2 + H2 ----> NH3
with Delta H = - or +66
and what was the answer?


Half it to +33 i think
I wonder if this thread can overtake the biology one
Original post by Abused Tampon
what did people get for the question about the enthalpy change of amonia? N2 + H2 ----> NH3
with Delta H = - or +66
and what was the answer?


there was no ammonia question....


u mean nitrogen monoxide to make nitrogen dioxide right?


NO + 02 ---> NO2 + O


and then nitrogen monoxide breaking down ozone:

NO + O3 --- NO2 + O2
NO2 + O ---- NO + O2
O3 + O ---- 2O2
Reply 747
Original post by EternalDoom
Hmmmmmmmmmmms, what did people put for why enthalpy change of formation was hard to calculate exactly? I said it was hard to perform under standard conditions


Only questions that were hard were the little 2-markers that havent come up in past papers


i put the energy is contained within the bonds themselves making it impossible to work out exactly, only the change to the surrounding breaking these bonds causes
Original post by Abused Tampon
what did people get for the question about the enthalpy change of amonia? N2 + H2 ----> NH3
with Delta H = - or +66
and what was the answer?


+33

You had to divide by 2 to per enthalpy change per mole
Original post by ChessMister
No, he means 2 methylpropan-2-ol


You don't have to put a 2 in front of the methyl on methyl propan-2-ol, because it only has 3 carbons the methyl can only go in one place (on the second carbon), otherwise if it was put on the first carbon the longest carbon chain would be 4, so it would turn into butan-2-ol.
I FAILED THE LAST QUESTION SO BADLY :angry: :mad:

BTW I HOPE ALCOHOL WORKS AS THE USES OF METHANOL :confused:
Original post by EternalDoom
there was no ammonia question....


u mean nitrogen monoxide to make nitrogen dioxide right?


NO + 02 ---> NO2 + O


and then nitrogen monoxide breaking down ozone:

NO + O3 --- NO2 + O2
NO2 + O ---- NO + O2
O3 + O ---- 2O2


Samesies! Boom!
Also, around -1270 can't remember exact. Ethyl Propanoate. Methylated spirits (probably wrong).

THe only question I was really unsure about was the 'how is IR spec used to analyse NOx in the atomosphere and other pollutants ect'?/
Original post by viksta1000
+33

You had to divide by 2 to per enthalpy change per mole


Ahhhh crap lost a stupid mark there....
Reply 753
Original post by viksta1000
+33

You had to divide by 2 to per enthalpy change per mole


:eek:

Great.........there goes another mark xD

I thought it was too easy, just transferring a number?! :mad:
Original post by racheatworld
You don't have to put a 2 in front of the methyl on methyl propan-2-ol, because it only has 3 carbons the methyl can only go in one place (on the second carbon), otherwise if it was put on the first carbon the longest carbon chain would be 4, so it would turn into butan-2-ol.


ahh
Isn't the enthalpy change of formation difficult to work out directly because elements have no enthalpy change of formation themself?

God, I shouldn't read these threads, it's so self-destructive. You always see where you misread a question or rushed an answer or made a stupid error!
Reply 756
ethylpropanoate is what i got for the ester :/ hope thats right

and for the enthalpy change would i loose the mark for putting +66 ?? or did it really have to be 33 :frown:((((
Original post by Awesomesauce
Samesies! Boom!
Also, around -1270 can't remember exact. Ethyl Propanoate. Methylated spirits (probably wrong).

THe only question I was really unsure about was the 'how is IR spec used to analyse NOx in the atomosphere and other pollutants ect'?/


I wrote it is used to find what functional groups are present in the pollutants, as the covalent bonds vibrate when a functional group is present.....


The small 2 markers really annoyed me
Reply 758
The other use of methanol methylated spirits?
For the last part will there be marks for the fragment ions that I found? even though i got the propanoic acid wrong :frown:

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