EdExcel Nuffield Unit 4 CHEMISTRY

haha i doubt it, i dont think i spelt it right tbh

Reply 21

OP

I picked Hypothesis 2 for the last Q.

For the 1st q i gave titration with sodium thio for Iodine, coloration of Iodine and Conductivity.

And all i remember is H2 Nickel cat, LiAlH4 , and that gives a OH group, if someone asks me the q's i might be able to remember what i put down.

Reply 22

mos what did you get for your rate determining step? and why?

what did the fact it wasn't saturated mean? i said 2 double bonds...only one i wasnt certain of in that bit

and was that thing acting as a base or acid?

Reply 23

OP

georgeElsworth

mos what did you get for your rate determining step? and why?

what did the fact it wasn't saturated mean? i said 2 double bonds...only one i wasnt certain of in that bit

and was that thing acting as a base or acid?

It was a base, pretty sure.

My RDS was screwed, H+ and that other alkane thing was both 1st order so i thought i might as well include both into my rate equation, i screwed up there.

Reply 24

yeh, well no one really knows what the rate thing was.

Did anyone here do chemical engineering?

Reply 25

ahezhara

I supported Hypothesis I. Did anyone else?

I think my reasoning was that because the ratio of acid to base was higher, one would expect a decrease in pH... and there was. Therefore the CO2 was making it more acidic, hence hypothesis I, blah blah blah.

Not sure about it though, I may have argued it circularly.

Reply 26

Hefina

well i just put hypothesis II just because hypothesis 1 said that CO2 would be evolved and the concentration of co2 went down after the exercise.

Reply 27

well my acid/base was decreased from before to after...which means a decrease in acid...so in theory the pH should have gone up. But it went down which was accounted for by the production of lactic acid

Reply 28

OP

Hefina

well i just put hypothesis II just because hypothesis 1 said that CO2 would be evolved and the concentration of co2 went down after the exercise.

Exactly!

Reply 29

i want to see the paper? can anyone get it..? some how they always get the maths 1

Reply 30

invisibleforest

Hang on hang on … I thought q2 was second order? Like with propanone and H+ in the rds?

I got confused because the double bond in the propanone doesn’t break so I was like “huh? Wtf does the hydrogen dooo?”

My long chain compound thing was

CH3CH2CH2CH=CHCHO

… or something like that. and I hydrogenated it (nickel catalyst etc) and then added lithium aluminium hydride to get an alcohol group?

&& buffer question. *DIES*

I said hypothesis 2 because concentration of hydrogen carbonate and CO2 went down in the reaction … and because they gave us loads of space I ranted on about buffers and those equations where adding H+ changes position of equilibrium etc …

Unit four was just haaard. I hope synoptic is okay! :s

Reply 31

Formica

1

Anyone else get trans-2-hexenal for the alarm pheromone?

Reply 32

invisibleforest

Formica

Anyone else get trans-2-hexenal for the alarm pheromone?

edit. yes i did. LOL i remembered i did but an aldehyde group ... can't remember if it was trans or cis but I just put whatever was in the question. :smile:

Reply 33

we didnt have to name it newhere tho did we?

Reply 34

for turning it into an alcohol, did it say there are two stages to change it to ...... for one of these stages give the reactant and catalyst?

so hydrogen the reactant and nickel the catalyst...OR LiAlH4 and catalyst?

Reply 35

OP

georgeElsworth

we didnt have to name it newhere tho did we?

LMAO yeah i could've sworn we didn't need to name it :s-smilie:

Reply 36

haha i had to think about what they were talking about, it was a different language for a few mins

Reply 37

OP

georgeElsworth

for turning it into an alcohol, did it say there are two stages to change it to ...... for one of these stages give the reactant and catalyst?

so hydrogen the reactant and nickel the catalyst...OR LiAlH4 and catalyst?

LiAlH4 doesn't need a cat, but H2 definitely does.

Reply 38