F334 (19/06/2013 9:00AM) - Salters Chemistry (Chemistry of Materials) Revision Thread

For the E/Z isomer thingy I got this:

I think something like this came up in the Jan 2013 F335 paper...

Reply 282

Original post by _Mollie_

Would the plastic bottle just melt in the absence of oxygen?

Yup! I put melt into a liquid :smile:

Reply 283

EdwinLo

Original post by abzy1234

The colour of potassium manganate is purple, and the end point is when it turns the first (permanent) pale pink colour. This came up in June 2011 if I can remember, plus somewhere in a legacy

Hmm, I think it was two carbons though right? Yeah I'm pretty sure it was two carbons... Plus there wasn't any absorption for spectrum A above 2500, so there wasn't any OH bond. I think that's what it was :smile:

Yeah my bad I'm thinking of a different question where butan-1,4-diol was the answer, you're right. Also I know I'm wrong about putting a carboxylic acid that was dumb. Do you think I'd get a mark for saying that there was a C=O peak at whatever wavenumber that is for compound A?

Reply 284

http://www.youtube.com/watch?v=eVomKthCP_k

Reply 285

MTI

Original post by Kreayshawn

all old boundaries for you guys:

F334: Materials
100% - A - B - C - D - E - U

January 2010
Raw 90 64 56 49 42 35
UMS 90 72 63 54 45 36

June 2010
Raw 90 64 56 49 42 35
UMS 90 72 63 54 45 36

January 2011
Raw 90 63 56 49 42 35
UMS 90 72 63 54 45 36

June 2011
Raw 90 68 61 54 47 40
UMS 90 72 63 54 45 36

January 2012
Raw 90 63 57 51 46 41
UMS 90 72 63 54 45 36

June 2012
Raw 90 63 56 50 44 38
UMS 90 72 63 54 45 36

January 2013
Raw 90 71 64 57 51 45
UMS 90 72 63 54 45 36

wow it was high in January this year :s-smilie:

do you think it will be similar for this one?

Reply 286

Original post by EdwinLo

Yeah my bad I'm thinking of a different question where butan-1,4-diol was the answer, you're right. Also I know I'm wrong about putting a carboxylic acid that was dumb. Do you think I'd get a mark for saying that there was a C=O peak at whatever wavenumber that is for compound A?

Yeah you'll get that mark don't worry :smile:

Reply 287

EdwinLo

Original post by abzy1234

For the E/Z isomer thingy I got this:

I think something like this came up in the Jan 2013 F335 paper...

Do you think it's ok to draw the hydrogens on, in the inside of the ring as in cis/trans isomerism shape, same as yours otherwise but without wedges?

Reply 288

Original post by EdwinLo

Do you think it's ok to draw the hydrogens on, in the inside of the ring as in cis/trans isomerism shape, same as yours otherwise but without wedges?

Hmm am not too sure, as that means you'll have part skeletal and part full structural. Don't worry, I expect the examiners to be lenient for this question as it was perhaps one of the hardest parts of the paper :smile:

Reply 289

Original post by MTI

wow it was high in January this year :s-smilie:

do you think it will be similar for this one?

I think it will. But we have no idea how everyone did across the country, so we'll just have to wait and see. Compared to the Jan paper, I think this was a broadly similar paper :smile:

Reply 290

Original post by abzy1234

The colour of potassium manganate is purple, and the end point is when it turns the first (permanent) pale pink colour. This came up in June 2011 if I can remember, plus somewhere in a legacy

Hmm, I think it was two carbons though right? Yeah I'm pretty sure it was two carbons... Plus there wasn't any absorption for spectrum A above 2500, so there wasn't any OH bond. I think that's what it was :smile:

http://www.youtube.com/watch?v=eVomKthCP_k

If I say the solution turns from colourless to pink will i get marks?

as the Mno4 disappears to colourless as in the video

Reply 291

kezeyer

What did everyone get for the orders question? They're usually really easy but I got confused by the RDS bit afterwards. :s-smilie:

Reply 292

Orders:

Did everyone get 1st for Ch3Cl or whatever

2nd for H2o

RDS was step 2 and was wrong as it didn't contain water, which was in the rate equation and so in the RDS

Reply 293

Original post by aWildPidgey

http://www.youtube.com/watch?v=eVomKthCP_k

If I say the solution turns from colourless to pink will i get marks?

as the Mno4 disappears to colourless as in the video

If you look at June 2011 Q4bi, it's an almost replica of today's question. In the mark scheme they write:

1. (fill) burette with KMnO4 / MnO4– solution
2. use bulb / volumetric / graduated / 25 cm3 / 10 cm3 pipette for...
3. to place solution in flask / beaker and then acidify (and warm flask)
4. then add KMnO4 / MnO4– solution slowly (AW) near end point
5. until permanent pink colour AW

I think it will only turn colourless if you put the MnO4 in the conical flask, the other way around from what they would expect I think. I don't think you'll drop that mark if you say that you put the MnO4 in the conical flask then... :smile:

Reply 294

Bonnbbb

Original post by kezeyer

What did everyone get for the orders question? They're usually really easy but I got confused by the RDS bit afterwards. :s-smilie:

I got zero for the first one and second for the one underneath. What did you get?? Not sure if i got that one right it took me ages to figure out!

Reply 295

Question was about why the mechanism/equation was wrong wasn't it???

Reply 296

Original post by Bonnbbb

I got zero for the first one and second for the one underneath. What did you get?? Not sure if i got that one right it took me ages to figure out!

I got one and then two...

For the rate determining step I said that two moles of water react in the fast step reaction to give an intermediate, which can go onto react with halogenoalkane.

I'm really not sure on that; it was quite a weird kinetics question :smile:

Reply 297

Another

21

Original post by abzy1234

For the E/Z isomer thingy I got this:

I think something like this came up in the Jan 2013 F335 paper...

I got this too! Except I also drew lines in for the hydrogen atoms. The only reason why I remember this is because I viewed a video about this type of Isomerism in November... absolute miracle I remembered it.

Original post by kezeyer

What did everyone get for the orders question? They're usually really easy but I got confused by the RDS bit afterwards. :s-smilie:

H2O of order 2, CH3Cl of order 1, overall three. I was super confused about this as well - who the hell practically raises their concentrations of a solution by 1.5? If anything, the investigation taught me that even doubling your concentrations are hard enough.

For the second bit - CH3Cl was part of the rate equation, therefore the rate determining step, therefore it must be involved in the slow reaction.

Also added a bit on saying the ions [OH-] and [H+] are going to be incredibly unstable in the gaseous state, so any reaction involving them must be fast.

Original post by aWildPidgey

goes from colourless to pink doesn't it?

MnO4- is purple in colour. The only reason why I remembered that is because my new Chem teacher was hell bent on doing EVERY SINGLE PRACTICAL in the textbook.

(edited 10 years ago)

Reply 298

kezeyer

Original post by aWildPidgey

Orders:

Did everyone get 1st for Ch3Cl or whatever

2nd for H2o

RDS was step 2 and was wrong as it didn't contain water, which was in the rate equation and so in the RDS

Yeah, that's what I got. But I thought the RDS bit ask how it supported the orders, so I wrote about CH₃Cl being involved or something? I don't know, definitely messed up that part anyway. Ah well!

Reply 299