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OCR F324-June 2013 Chemistry

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Reply 940
Avatar for otrivine
otrivine
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Original post by MathsNerd1
Isn't it just a solvent? And isn't it the phase that moves in chromatography?


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yes correct ! but you have to be more specific though

my turn :smile:
Original post by otrivine
I finished revision and just doing papers, like legacy :smile:

Define Rf


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Original post by otrivine
yes correct ! but you have to be more specific though

my turn :smile:


Would ethanol work?

Explain how HLPC works (4)


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Reply 943
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otrivine
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14
Original post by MathsNerd1


yup!

my turn
Reply 944
Avatar for otrivine
otrivine
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14
Original post by MathsNerd1
Would ethanol work?

Explain how HLPC works (4)


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is this another word for GC-MS
Reply 945
Avatar for zxcmnb
zxcmnb
Original post by ak_bang
Errrrr well UMS grade boundaries are already fairly high due to the fact that 90% of students recieve help from their teachers. Do you expect students like me, who have to do the practicals under exam conditions, to sit here while everyone else seems to have an unfair advantage? I don't think so love


stop getting emotional
Original post by otrivine
is this another word for GC-MS


HLPC is high liquid pressure chromatography, do you know the process for it?


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Reply 947
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otrivine
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Original post by MathsNerd1
HLPC is high liquid pressure chromatography, do you know the process for it?


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Have no clue whats so ever :colondollar:

Did I miss a page in the book :confused:
Original post by otrivine
Have no clue whats so ever :colondollar:

Did I miss a page in the book :confused:


Maybe it's not asked about then, what about column chromatography?


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Reply 949
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otrivine
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14
Original post by MathsNerd1
Maybe it's not asked about then, what about column chromatography?


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yes column chromatogrppahy is to do with Gas chromatography

please tell me what is HPC thingy:confused: worried now
Original post by otrivine
yes column chromatogrppahy is to do with Gas chromatography

please tell me what is HPC thingy:confused: worried now


1) Sample if dissolved into suitable solvent
2) Added to the top of a column a liquid eluent (mobile phase)
3) This mobile phase is then forced through the column via pressure
4) The different components of the sample has different strengths of interaction with the stationary phase.
5) Therefore time varies with samples - the time taken for a particular sample is called the "retention time" and is a unique characteristic to that particular sample

You can check with a data base to see what type of compounds the sample contains :smile:
Reply 951
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otrivine
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14
Original post by posthumus
1) Sample if dissolved into suitable solvent
2) Added to the top of a column a liquid eluent (mobile phase)
3) This mobile phase is then forced through the column via pressure
4) The different components of the sample has different strengths of interaction with the stationary phase.
5) Therefore time varies with samples - the time taken for a particular sample is called the "retention time" and is a unique characteristic to that particular sample

You can check with a data base to see what type of compounds the sample contains :smile:



is this in ur syllabus for edexcel?
Original post by otrivine
yes column chromatogrppahy is to do with Gas chromatography

please tell me what is HPC thingy:confused: worried now


Basically and it's nothing to worry about if its not in the book, I've been using knockhardy and its on there so that's why I asked.


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Reply 953
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otrivine
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Original post by MathsNerd1
Basically and it's nothing to worry about if its not in the book, I've been using knockhardy and its on there so that's why I asked.


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OK :smile:

Suggest a use for NMR (1)
Original post by posthumus
1) Sample if dissolved into suitable solvent
2) Added to the top of a column a liquid eluent (mobile phase)
3) This mobile phase is then forced through the column via pressure
4) The different components of the sample has different strengths of interaction with the stationary phase.
5) Therefore time varies with samples - the time taken for a particular sample is called the "retention time" and is a unique characteristic to that particular sample

You can check with a data base to see what type of compounds the sample contains :smile:


Yes :colondollar: Sorry if I'm trespassing :biggrin:
Original post by otrivine
OK :smile:

Suggest a use for NMR (1)


To identify compounds within a substance?


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Reply 956
Avatar for otrivine
otrivine
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Original post by MathsNerd1
To identify compounds within a substance?


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Yes good

my turn
Original post by otrivine
Yes good

my turn


Okay, explain why TMS is used as the reference substance in NMR? (2)


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Reply 958
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otrivine
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14
Original post by MathsNerd1
Okay, explain why TMS is used as the reference substance in NMR? (2)


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because TMS is used standard because it has a chemical shift of 0ppm and so could be used for comparison with other chemical shift peaks which are greater than 0ppml
Original post by otrivine
because TMS is used standard because it has a chemical shift of 0ppm and so could be used for comparison with other chemical shift peaks which are greater than 0ppml


I was thinking because its got 12 hydrogens in the same environment making it the most stable, therefore putting it as the standard. But what you said was correct too.


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