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

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we shall see what the ms says
but i'm not sure though... it asked "large scale use of methanol", therefore i may be wrong coz obviously no one drinks methanol as it is a KILLER

Yeah, I asked my teacher after and he said the answer was probably to use it in biofuels. Also googled it and you could probably have put making methyl esters for perfumes etc too.

Reply 961

Flint_09

Original post by NRT

Sorry im not too sure i think it was complete first. But im seriously 50/50 it was only 2 marks so don't worry too much about it.

i would say do worry about it, lol coz all there were 10s of the 2 mark questions all over the paper. so adding them up makes an immense difference, ONLY if u think just this 2 marks but not the rest

Reply 962

eagles!

i thought overall this exam went pretty well
last time i got a d though

Reply 963

vfest

just seen tht i completely messed up the first 10 marker! :frown:

Reply 964

montanaj

Original post by vfest

just seen tht i completely messed up the first 10 marker! :frown:

Don't worry too much, there's no going back now :P What did you put? Maybe you gained a few marks?

Reply 965

Flint_09

Overall i would say the exam was good, but only few 1 MARKER AND 2 MARKER questions were misleading.

Reply 966

Davidragon

Lol at this exam. The closed system is a point I didn't get which was a good one :/

Reply 967

broken_glass_heart

Original post by montanaj

Don't worry too much, there's no going back now :P What did you put? Maybe you gained a few marks?

i missed both 10 markers! am worser than u

Reply 968

vfest

Original post by montanaj

Don't worry too much, there's no going back now :P What did you put? Maybe you gained a few marks?

i did the curly arrows bit and then the reaction and the fission but then i said about polarity but then i also said that the bond enthalpy of C-Cl was less than that of C-Br

Reply 969

The medjai

For the first 10 marker was Nucelophillic substitution the mechanism?

Reply 970

vfest

Original post by broken_glass_heart

i missed both 10 markers! am worser than u

ooohh! did u run out of timee??

Reply 971

The medjai

Original post by vfest

i did the curly arrows bit and then the reaction and the fission but then i said about polarity but then i also said that the bond enthalpy of C-Cl was less than that of C-Br

But bond enthalpy decreases down Group 7.

Reply 972

shooby_doo

Original post by The medjai

But bond enthalpy decreases down Group 7.

No its the other way round i think

Reply 973

broken_glass_heart

Original post by vfest

ooohh! did u run out of timee??

yeh sooooo badly,

Reply 974

The medjai

Original post by shooby_doo

No its the other way round i think

But the C-Br bond is broken more easily than C-Cl.

Reply 975

Phenylethylamine_

Original post by shooby_doo

No its the other way round i think

Bond enthalpy does decrease down the group, that's why the C-Br bond is weaker and can break more easily than the C-Cl bond, even though the C-Cl bond has greater polarity but bond enthalpy is more of a important factor influencing rate of hydrolysis :smile:

Reply 976

shooby_doo

Original post by lolo-x

fairplay... although you wouldn't class petrol or vinegar or something else disgusting as a drink, although in theory you can drink them, so idk if that argument works.. haha

Source from wiki
Applications for methanol:
"In a soda to be mixed with water to obtain a very low alcohol drink or pure (brand Ricqlès which contains 80% alcohol in France). The alcohol is also used to alleviate nausea, in particular motion sickness, by pouring a few drops on a lump of sugar."

So technically we're right! :P lol

Reply 977

NRT

Basically, C-Cl bond is the shortest and therefore requires the most energy to break, C-Br is longer. Therefore hydrolysis of the Chloropropane or whatever it was took longer.

Reply 978

shooby_doo

Original post by Phenylethylamine_

Wait !
I thought that an increase in bond enthalpy means that it means the bond is stronger :confused:

I got the concept of it that bond enthalpy's are more of an important factor ... But i said that bond enthalpies increase down the group ... :/

Reply 979

Thompson93

In the nucleophilic substitution i showed K. So I showed the OH breaking off from the K etc. Will I still get the marks? It meant that I ended up with KBr :s-smilie: