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OCR A Chemistry F322 Chains, Energy and Resources Thu 19 Jan 2012

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Reply 440
Original post by faz_341
what was the emperical formula for a cycloalkane with 6 carbons then? is it not Ch2


it is :wink:
Original post by Eternal Rest
Also, what did people get for the CFCs being hydrolysed question?

I put it doesn't have hydrogen so it can't make hydrogen bonding, is that right?


Yepppppp!
No O-H bonds so can't form H bonds with H20 molecules!
Reply 442
Original post by Tyles
it is :wink:


Woo!
did anyone get 431.5 for bond enathlp of hcl?
Original post by Conal09
What did anyone get for the Sulfuric acid percentage yield question?? I got 94% but really had no idea...


Yuuppp! Got the same.
Reply 444
Original post by maryam.asmari
Yepppppp!
No O-H bonds so can't form H bonds with H20 molecules!


i put no oh group in molecule so cant bond hydrogen bond with water dyu think id get the mark?
Original post by faz_341
Woo!
did anyone get 431.5 for bond enathlp of hcl?


I got +584, but I'm probably wrong lol.

Can you tell me how you worked it out please?
Original post by Eternal Rest
Oh yeah, what did people get for the empirical formula question?
I got C6H12 but wasn't too sure. :/


Doesn't empirical formula mean simplest? I put CH2 :s-smilie:
The sulfuric % yield IS 94% but im sure they will accept 93%
Original post by maryam.asmari
Doesn't empirical formula mean simplest? I put CH2 :s-smilie:


I put CH2 at first but I thought it's impossible for one carbon atom to be cyclic. :s-smilie:
Original post by faz_341
i put no oh group in molecule so cant bond hydrogen bond with water dyu think id get the mark?


I think you should do! Unless they penalize you on 'Hydrogen bonding'. Don't think they would do. But it came up on a past paper and it did say H bonding, because that's the whole point of the OH to bind with H in H20 :s-smilie:. Hopefully they don't penalize you though.
Reply 450
Original post by Eternal Rest
I got +584, but I'm probably wrong lol.

Can you tell me how you worked it out please?


679 + ? = -184
so ? equals 862
since there is 2hcl divide by two = 431.5
Reply 451
Original post by faz_341
Woo!
did anyone get 431.5 for bond enathlp of hcl?


correct.

Always work backwards to check your result..

431.5 x 2 = 863
863 - 184 = 679

679 was the total of the reactants.
Original post by Eternal Rest
I put CH2 at first but I thought it's impossible for one carbon atom to be cyclic. :s-smilie:


I'm don't know anymore. I'm pretty sure it is CH2. They DIDN'T* say 'make sure the empirical formula is also cyclical'. It's just the simplest whole number ratio.?
(edited 12 years ago)
Original post by Tyles
correct.

Always work backwards to check your result..

431.5 x 2 = 863
863 - 184 = 679

679 was the total of the reactants.


did you get -134 kjmol-1 for the answer on the mg thing one?
Reply 454
empiracal is simplest whole number ratio so its CH2
Original post by faz_341
679 + ? = -184
so ? equals 862
since there is 2hcl divide by two = 431.5


I added Cl2 and H2, then took 184 from the total.

Then I divided the answer by 2, and got +584.

I've probably got it wrong lol.
Reply 456
Original post by otrivine
did you get -134 kjmol-1 for the answer on the mg thing one?


yes i did -2.68/0.02 i think
what i founbd weird fore this was it said answer must be in 3 sig fig and answer was already in 3sigfig
Original post by faz_341
yes i did -2.68/0.02 i think
what i founbd weird fore this was it said answer must be in 3 sig fig and answer was already in 3sigfig


exacly hahaha and did you get for part a ) 2.6753 something cause i did the 50+0.05 ? and for the question on suggest why cfc banned but still there are i wrote of planes release cfcs and cars when release exhaust fume contains cfc?
can you say for the bit about why cfcs dont hydrolise with water, because of the polarity of the c-f and c-cl bonds, repel the OH?!?!?!
and for the energy question where you had to work out the Q = MxcxdeltaT, and then work out the number of moles(which was 0.02).. and then the next question you had to divide Kj/moles..did you times your answer by two? because in the jan 2011 paper, it was a similar question and you had to times by 2 :s-smilie:
I got CH2. I thought this was a well balanced paper compared to previous ones. No 10 markers!

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