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

Scroll to see replies

Reply 1140

rawr4more

Original post by _Say_Goodbye_

Hmm, looks like i only did 5 questions :s-smilie:

FML. I thought the hydrogen just added across the C--C double bond and so it stayed cyclic.

oooo i chained it =/ but knowin me im wrong =/

Reply 1141

darkxangel

Original post by rawr4more

oooo i chained it =/ but knowin me im wrong =/

same

Reply 1142

_Say_Goodbye_

Original post by rawr4more

oooo i chained it =/ but knowin me im wrong =/

Hahaha okay, now I literally have no idea. Retake in January should be nice :frown:

Why do you think it would go straight chained? There must be something good behind that!

Reply 1143

soph2149

Hello there.

Does anyone have a rough guess of how many marks you would lose on the 'compound x y z' question if you worked out the structures for x and y but completely missed out the structure for z? I had no answer for that because I didn't actually notice that they asked for the structure of the ester too....*facepalm*

Also how many marks would you lose for the nucleophilic subsitution of chlorine and bromine question if you got the whole question right apart from the 'which reaction would have fastest rate' or something like that. I had learnt this so well but for some reason my brain had shut down towards the end of the paper and decided to put the chloroalkane would give the fastest rate. But then I gave the right reason, which was that the C-I bond was weaker than the C-Cl bond. So I had the wrong answer but correct explanation *second facepalm*

And there was no question 8 right? Please say there was no question 8....

Reply 1144

sj1994

there was no question 8!

Reply 1145

rawr4more

Original post by _Say_Goodbye_

Hahaha okay, now I literally have no idea. Retake in January should be nice :frown:

Why do you think it would go straight chained? There must be something good behind that!

i just drew a sketal heptane =/

Reply 1146

racheatworld

Original post by StrawberryKoi

The X Y Z question was the last one. I remember because I had to continue the answer onto the next page which was one of those additional pages at the end.

Ah thanks. I was panicky for a second there!

Original post by _Say_Goodbye_

I literally have no idea!! I just did the last part of question 6, with 3 boxes where you had to draw the products and thought it was the end of the paper, sorry if I'm worrying you aha but yeah I just wondered how many guaranteed marks I've lost... I think it must have been more than 10, maybe 20+

No its fine! Well, the question 6 you're describing was actually question 5, question 6 was about green chemistry, so I think you missed that and the X, Y, Z question out.

Reply 1147

_Say_Goodbye_

The question 8 thing was started by me. I didn't do any questions after the 'chlorine bromine' one ones because I'm an idiot, and i thought that was question 6 and there were 2 questions after it. However apparently that was Q5 which means I'm even more stupid than I thought and there were 2 questions after that, 6 and 7 so you're fine. I'm guessing you would get 8, but surely you meant C-Br was weaker than C-Cl aha. I'll leave the first to someone else who's done that question :wink:

Reply 1148

racheatworld

Original post by timdr

Question 5, did it stay as a cyclic.or go to a chain when you added hydrogen gas?!

It stayed cyclic, the double bond broke and the 2 carbons that were in the double bond each had an extra Hydrogen on them.

Reply 1149

_Say_Goodbye_

Thanks racheat world! Yes I did, so I'm guessing that was 20+ marks lost :eek:

I hate my stupid brain, just what was I thinking?? Resit in January, I swear I only needed like 70% too :angry:

Reply 1150

sj1994

do you reckon i will still get a mark for use of methanol as "it can be used in spirits"
???

Reply 1151

racheatworld

Original post by soph2149

On the X, Y, Z question for not putting the ester I'd say you'd lose 2 marks? Which is nothing really, as I think the bulk of the marks for the question will be for referring to the Infra-red and Mass spectrum peaks to determine X and Y, as this is what the majority of my answer was. The ester was just to test your knowledge of reactions with alcohols, so I doubt you've lost many marks there.

And for your nucleophilic mistake, I'm really unsure as to whether you'll get the mark for your C-I bond is weaker than C-Cl explanation (even though that is correct) because you've contradicted it by saying that C-Cl has a faster rate. My tutor says that if you contradict yourself with 2 answers, the examiner doesn't know which one you mean and so they'll just mark it as wrong. Having said that, that's usually if you draw something right and name it wrong, so I have no clue if you'll get that mark. If you lose the marks for that, I think you'll lose about 2-3 marks maximum, so nothing to really worry about.

Reply 1152

rawr4more

btw i know this is kinda off topic but does anyone know what happens to papers that go through special consideration like are how they marked or what they do?

Reply 1153

darkxangel

Work out enthalpy change of formation -1279

Why can enthalpy change of formation not be measured directly?
high activation, more than one product...

In terms of rate of reverse reaction and rate of forward reaction, explain how the mixture reaches dynamic equilibrium: rate of forward reaction is the same as the rate of backward reaction.

same temperature but a higher pressure: same amount of moles in each side, collision theory,

Why cannot it reach equilibrium in a car engine?
not a closed system, temp. not high enough,

What is enthalpy change of formation /2 = +33

NO has is a radical, what does it tell you about the molecule?:
has a free electron to give away or something

Draw a tertiary alcohol of C4H10O
Name it:

CH3
CH3-C-OH
CH3

Draw the alcohol that can be oxidized to make butanone
2-methyl ethanol i think.

How does it break down ozone?
NO+O3-->NO2 + O2
NO2+O3-->NO+202
203+O2-->4O2

NO acts as a catalyst

Which one is cracking
5 i think

Which does not have 100% atom economy:
1 think,

Which forms structural isomers

Fermentation & atom economy & percentage yield
could say either one if you explained why

For the nuclear substitution i got: something OH+KBr
-The substitution of Br would be faster, because the C-Br bond strength/enthalpy is weaker than the C-Cl bond.
-it was heterolytic fission

Shape question:
tetrahedral, because electron pairs repel each other and go as far apart as possible.
next one was trigonal planar,

complete combustion:
CH3OH+1.5O2-->CO2+2H20

Incomplete combustion:
CH3OH+O2-->CO+2H2O

Question 5: add H2 to the double bond
2 isomers of adding HBr across methyl-cyclohexene double bond

another use for Methanol question:
feedstock for chemical processes

Name alkene used to make polymer: but-1-ene

What do CO and HCl do to environment, what are chemists doing to minimize damage?

CO:'greenhouse-effect/global warming', adding to carbon footprint, toxic, reduces the ability of blood carrying oxygen
HCl:acid rain, irritant-harms environment,
finding a use for CO-
HCl can be used as a catalyst-which i'm not so sure about, to neutralise over-alkaline soil for agriculture,

Importance of international protocol agreements?
Put down something about communicating and educating other countries who are not aware of impacts of high carbon emission to reduce global-warming. Since i didn't revise this bit i made up a lot rubbish. :/

alcohols liquid question:
alcohols have hydrogen-bonding because of OH groups which is stronger than van der waals forces.

A Functional group: is a group attached to and organic compound and determines its chemical properties.

dissolve water question:The reason why poly methanol dissolves in water is because it hydrogen bonds with it.

For the last question I wrote down the formula not the names-can't quite remember the answer, but you had to work out the empirical formula and then times it by two o find a carboxylic acid for X-C3H8O2>>it was something like this i think.
For Y the peak was at 46. You had to find the formula of an alcohol i think.
For Z you would just write an equation and the right formula for the ester.

some of this might be wrong and it's not in order either. :colondollar:

(edited 12 years ago)

Reply 1154

Rosi M

Original post by sj1994

do you reckon i will still get a mark for use of methanol as "it can be used in spirits"
???

Haha i wrote that. Methylated spirits. I was stuck on that.

You know the long marker on hydrolysis of halogenoalkanes, im so stupid. Would i get a mark for writing this: CH3CH2CH2CL + KOH ---> CH3CH2CH2OH + CL- + K+

I wrote K+ ? I should have wrote KCL. Any hope?

Reply 1155

darkxangel

Original post by Rosi M

i did both, but you will probably still get the marks unless the mark-scheme is really mean, but most people ignored the K completely so don't worry :h:

Reply 1156

Rosi M

Original post by darkxangel

i did both, but you will probably still get the marks unless the mark-scheme is really mean, but most people ignored the K completely so don't worry :h:

Thanks so much! I was thinking about that yesterday too when i rememberd! Lets hope the mark schemes nice.

Reply 1157

peace345

Original post by *Funky-buddha*

Darn it TSR seems to be losing its touch. Usually, there would have been the full unofficial mark scheme and/or scanned papers of the exam up by now :P

haha i agree!

Reply 1158

Tasha001

Original post by Abused Tampon

..............................

yeah it was 46. i spent ages trying to find how it would be 47 :confused:

Reply 1159

king1234

how many questions where they after that electrophillic question guy next to me missed out all questions ater that thought the exam paper was finished,