Edexcel Chemistry Unit 6A Practical - June 2006

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Reply 80

ATESalisbury

21!?!? bloody hell!

Reply 81

Mustard-man

technically 20 now, because i took an exam on thurdays

Reply 82

Smashingdude

Thanks alot MizFizz. However can i thank you?

Reply 83

ATESalisbury

Smashingdude

Thanks alot MizFizz. However can i thank you?

Rep her!

Reply 84

genie k

hii.does any1 have any notes 4 this unit that they cn put up?

Reply 85

mizfissy815

why not? After that unit 3A practical (after messing up last year's methyl orange indicator titration) I feel hyped, can't wait!

Personally, practicals aren't really a big problem for me. I'm a little more worried about the synoptic paper.
I can't say I've ever been hyped up for an exam before, except for last years AS math exams(and maybe physics). At the moment I'm a little more than worried about the W2 paper.

Reply 86

Mustard-man

Oh yeah, the 6B paper is actually hard :redface:

The massive calculation questions :redface:

, also they are so picky with the answers. So what might be accepted in the mark schemes of other units, may not necessarily get you full marks for the synoptic (you probably don't know what I'm talking about)

Reply 87

mizfissy815

The massive calculation questions , also they are so picky with the answers. So what might be accepted in the mark schemes of other units, may not necessarily get you full marks for the synoptic (you probably don't know what I'm talking about)

Calculations have always been strong suit of mine, so that really isn’t much of a problem. I just can't handle some of those 5 mark questions. I put everything I know down only to find out most of it is irrelevant and I missed out what I did need to put down. Plus, I like the old format of the papers better. You, know the essay type looking ones.

Reply 88

Mustard-man

For example, give me the reagents and conditions for a nucleophilic substitution of a halogenoalkane.

Reply 89

mizfissy815

For example, give me the reagents and conditions for a nucleophilic substitution of a halogenoalkane.

There are 3 different ones right? To form an alcohol, a nitrile and an amine?

Reply 90

Mustard-man

mizfissy815

There are 3 different ones right? To form an alcohol, a nitrile and an amine?

to form an alcohol

Reply 91

mizfissy815

What about the other 2? They can formed from haloalkanes through nucleophilic substitution as well...right?

Reply 92

Mustard-man

yeah, just answer the question

give me the reagents and conditions for a simple nucleophilic substitution of a halogenoalkane to give an alcohol

Reply 93

mizfissy815

yeah, just answer the question

give me the reagents and conditions for a simple nucleophilic substitution of a halogenoalkane to give an alcohol

Fine, gosh...

Reagents- NaOH
Conditons- heat under reflux in an aqueous solution.

Reply 94

Mustard-man

mizfissy815

Fine, gosh...

Reagents- NaOH
Conditons- heat under reflux in an aqueous solution.

In a synoptic paper that would of got you 1 out of 2 marks.

This is what I'm talking about, synoptic papers require a little more. For 2 marks you needed to say you 'acidify' at the end. I didn't know this, but this question came up last year :redface:

Reply 95

mizfissy815

eckkk...
This sucks...

Reply 96

mizfissy815

NMR-

Nuclear Magnetic Resonance Spectroscopy provides us with detailed information about the nuclei of certain atoms. Hydrogen nuclei behave differently in different molecular environments; NMR tells us what the environments are and how many protons (or ¹H nuclei) are present in each.

For every type of molecular arrangement (molecular environment), there is a very slightly different magnetic field. The ¹H nuclei in these different environments have different energy gaps (delta E) between their high and low energy levels, and so absorb different frequencies of radiation. They are therefore given different NMR peaks and we can find out how many hydrogen atoms of different types are present in the molecule.

Every molecule will emit a different number of frequencies in an NMR machine. This results in a spectrum trace being formed. This spectrum trace will have peaks for each of the different types of hydrogen present. If there is more than one hydrogen with the same chemical environment, than the peak will be higher. Say there is a CH₃ group and a CHO…there will be only 2 peaks and their height ratio would be 3:1. This is because in CH₃ there are 3 hydrogen with the same chemical environment and only one in CHO. Now in order to be able to tell what the different environments present are, we need a standard to compare with. TMS (tetramethylsilane) has been chosen as standard reference because it gives a sharp signal well away from most of the ones of interest to chemists. The extent to which a signal differs from TMS is called its chemical shift. TMS is set at a chemical shift at 0 and the shifts of other types pf protons can be found from reference tables such as the one found in-
http://www.wbateman.demon.co.uk/asa2sums/sum5.5/sum5.5.htm

You don’t have to learn these chemical shifts…everything you need in the exam will be given to you.
Using tables such as these you can tell what causes each peak and the number of hydrogens present can be found from the height of the peaks and the information given.

Reply 97

mizfissy815

UV and Visible Spectroscopy-

If a substance absorbs radiation in the visible region of the spectrum, then the light that reaches your eyes from the substance will be lacking in certain colours and so no longer appears white.
A colorimeter is a simple type of visible spectrophotometer. Colorimetry is used to measure the intensity of absorption of coloured compounds over a narrow range of frequencies; it provides a useful way of finding the concentration of coloured compounds.
The graph will show areas of high absorption and areas of low absorption. Anything before 400 nm is in the ultraviolet range and unless there is any other area of absorption, the substance will be white. If the area of absorption happens to lie in the violet-blue range, than the substance will be yellow-red in colour.

I hope that makes sense. :redface:

There really isn’t anymore I can add to the UV spectroscopy. It’s isn’t important and I have yet to see a question that involves this type of spectroscopy. It’s pretty useless really.

Hope you guys find this useful and good luck with your exams!

Reply 98

Smashingdude

Hey Miz. Thanks a lot for the notes. Hey i noticed u took Biology. So need any help in that? I still remeber quite of it not to mention i used to be very good at it. You can say sometimes without any doubt that Bio is the most difficult subject in Alevels. Thats wht i thought last year but thingz changed after seeing chemistry. Anywayz in Bio u need a lot of refrence work especially in W2 when they give u a touch of STATS as well. Ive got some W2 notes and papers. Ill send u to ur gmail account. Thats the best i can do for u now. Ive got some papers as well. Best of luck on 23 for W2.(remember dont mess up the calculations. They r worth many marks and the easiest in W2. And write as many Further work/Limitations as u can write. I use to write 10 (yeah seriously) u never know which one gets accepted. There is no negative marking in edexcel so be chill in ur writing. Also go through all the pracitcals in the modular books which r at the end of each chapters. They r helpfull u know like reaction timing, and TTC hydrogen acceptors etc...)