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OCR B Salters - F335 Exam - 15 June 2011

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Reply 280

ManPowa

Can someone go through the whole of GLC.. what will they look for if they do ask us tomorrow? Thanks :smile:

Reply 281

JamesPen

Original post by Conor 419

I advise Chemguide for anybody who's struggling with NMR. CI doesn't do a god job of explaining it.

I found that the CI was so confusing! Now i pretty much understand the graphs which is the main thing you need to learn from it. I usually find getting the ratio of peaks and number of proton environments difficult.

Reply 282

*Rainbow*

Original post by JamesPen

If you mean the benzene molecules then it should be conjugated. For each carbon on the structure look for how many bonds it has attached to it. If it has 4 then it will have no hydrogens and if it has 3 bonds then 1 hydrogen atom.

Have you got the June 07 paper? It's the first question on there...

Reply 283

pearlover

Original post by JamesPen

IM feeling okay for this exam. Done most of the past papers and it seems like the markschemes have a trend in answers so its best to stick with them.

what books did you revise from?

Reply 284

JamesPen

Original post by ManPowa

Can someone go through the whole of GLC.. what will they look for if they do ask us tomorrow? Thanks :smile:

G.L.C is basically used to find components of a mixture or seperate mixtures ready for Mass spectrometry.

It relies on the equillibrium that is set up when a component distributes itself between mobile phase and stationary phase. Higher affinity for the mobile phase the faster the component emerges.

Mobile phase= Inert Carrier gas

Stationary Phase = High boiling point liquid on a solid support packed into long thin column coiled into an oven

When a component emerges from the column its is registered as peak. Area un der the peak is proportional to the amount of that component in the mixture.

Retention time is the time taken for the compenent to emerge from the column.

Hope that helps

Reply 285

Conor 419

So wait, is Kw back on the mark scheme?

Reply 286

JamesPen

Original post by *Rainbow*

Have you got the June 07 paper? It's the first question on there...

I think i have it somewhere in the depths of my external hardrive. I will have a look for you :smile:

Reply 287

JamesPen

Original post by pearlover

what books did you revise from?

I mainly used OCR Salters revision guide.

Reply 288

supernovainthesky

Original post by ManPowa

Can someone go through the whole of GLC.. what will they look for if they do ask us tomorrow? Thanks :smile:

GLC!

It has a stationary phase which is a high boiling point liquid on a solid support. This is in the column. The mobile phase is a unreactive gas such a nitrogen. This goes into the column along with the sample. The detector then records the time taken for each component to come out of the column. This is known as retention time. The detector then records this on a chromatograph. The x axis is the time and the y axis is the response I think. The area under each peak tells you the amount of that component. The peak ratios tell you the ratio of the components. The more volatile the component the shorter the retention time.

Hope that helps :smile:

So Kw's back?

Can someone say exactly which papers are on the same syllabus, as I realise some of the older ones include stuff we don't need to know? Is it worth doing these all anyway, as the exam is in the afternoon we'll have a good few hours in the morning too.

Reply 291

pearlover

Original post by JamesPen

I mainly used OCR Salters revision guide.

did you use the cgp book at all?

Reply 292

AGM

Original post by Jamesrb

Yes, it is very worth doing them. The only differences are generally some of the equation stuff like Kp.

Reply 293

*Rainbow*

Original post by JamesPen

I think i have it somewhere in the depths of my external hardrive. I will have a look for you :smile:

Thanks

Reply 294

jakjakjak

Original post by Conor 419

So Kw's back?

Reply 295

beckyxo

Original post by Conor 419

So Kw's back?

my teacher said you gotta know that
Kw = [H+][OH-] = 1x10^-14

BUT

the spec says 'value will be given'.

All you'd have to do is find [H+] or something which is just rearranging the equation :smile:

Reply 296

beckyxo

also that is in mol2dm-3 at 298 K