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    the specimen paper was very hard
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    Could someone please explain chromatography to me in a simple way because my book is to detailed. Thank you.
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    Can someone explain interpreting titrations? Just like the steps please?


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    (Original post by Fishhy34)
    the specimen paper was very hard
    Can you link it please
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    (Original post by JazzyT17)
    Could someone please explain chromatography to me in a simple way because my book is to detailed. Thank you.
    I'll summarise the notes in my guide - paper or gas?

    Paper:

    1 - Solvent moves up paper.
    2 - Chemicals in sample dissolve and move between it and the paper. This sets up an equilibrium (where the two reactions are balanced).
    3 - In the mobile phase, the chemicals move UP the paper FROM the baseline WITH the solvent.
    4 - Before the solvent reaches the top of the paper, the paper is removed from the beaker.
    5 - Different chemicals in sample form different spots on chromatography paper (usually it's filter paper). Chemicals that are in the mobile phase for longer from spots further up the paper (obviously - since they are moving for longer).

    Any other problems (or if you want to know about gas chromatography or calculating the Rf values from chromatography) let me know and I can try to explain. I will try my best to help but I'm no C7 expert but I have been revising it for 2 days solid and explaining it helps me to understand too.

    (Original post by lyricalvibe)
    Can you link it please
    There's two!

    http://www.ocr.org.uk/Images/80682-u...accredited.pdf

    http://www.ocr.org.uk/Images/137265-...-c7-higher.pdf
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    (Original post by lyricalvibe)
    Can you link it please
    http://www.ocr.org.uk/Images/80682-u...accredited.pdf
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    (Original post by JasonBrown2K14)
    I'll summarise the notes in my guide - paper or gas?

    Paper:

    1 - Solvent moves up paper.
    2 - Chemicals in sample dissolve and move between it and the paper. This sets up an equilibrium (where the two reactions are balanced).
    3 - In the mobile phase, the chemicals move UP the paper FROM the baseline WITH the solvent.
    4 - Before the solvent reaches the top of the paper, the paper is removed from the beaker.
    5 - Different chemicals in sample form different spots on chromatography paper (usually it's filter paper). Chemicals that are in the mobile phase for longer from spots further up the paper (obviously - since they are moving for longer).

    Any other problems (or if you want to know about gas chromatography or calculating the Rf values from chromatography) let me know and I can try to explain. I will try my best to help but I'm no C7 expert but I have been revising it for 2 days solid and explaining it helps me to understand too.


    There's two!

    http://www.ocr.org.uk/Images/80682-u...accredited.pdf

    http://www.ocr.org.uk/Images/137265-...-c7-higher.pdf

    Thank you so much! could you also explain the Rf value and gas chromatography.Also do you know of any past papers for our spec? thanks.
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    How could they involve questions on the chemical process for a catalyst and producing chemicals?
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    (Original post by JazzyT17)
    Thank you so much! could you also explain the Rf value and gas chromatography.Also do you know of any past papers for our spec? thanks.
    OK past papers for our spec: There are the two specimens I linked to in my post above and that's it.

    But fear not basically a lot of the content from the legacy papers is still relevant. I uploaded the 2008, 2009, 2010 and 2011 papers and markschemes in this thread: http://www.thestudentroom.co.uk/show...9&postcount=10

    Ignore question 1 because we won't be tested from anything related to a source book.


    Rf values:

    Rf = distance travelled by SOLUTE / distance travelled by SOLVENT

    Measure from the baseline of the chromatography paper to the spots.

    And that's pretty much it.


    Gas Chromatography:

    Mobile phase: Unreactive gas, eg nitrogen
    Stationary phase: Viscous (thick) liquid, eg an oil

    1 - Unknown mixture injected into long tube coated on the inside with the STATIONARY PHASE.
    2 - Mixture moves along tube with MOBILE PHASE until it comes out at the other end. Substances distributed between the phases (like in paper and thin-layer chromatography, too).
    3 - The time it takes a chemical to travel through the tube is called the RETENTION TIME.
    4 - Retention time can be used to identify different chemicals since the retention time is unique.

    Chromatogram for gas chromatography is a graph.

    They look a bit like this if you are unfamiliar with them:



    Each peek on the graph represents a different chemical.

    Distance along the X axis is the retention time - this can be looked up to identify the unique chemical.

    The peak height on the graph shows how much of that chemical was in the sample.


    And thin layer chromatography is just like paper chromatography, but instead of paper being used as the stationary phase, a thin layer of solid is used instead. A good example is silica gel on a glass plate.

    Mobile phase is again a solvent, just like paper chromatography.

    And I think that is just about everything you need to know about chromatography!

    Hope I helped!
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    (Original post by JasonBrown2K14)
    OK past papers for our spec: There are the two specimens I linked to in my post above and that's it.

    But fear not basically a lot of the content from the legacy papers is still relevant. I uploaded the 2008, 2009, 2010 and 2011 papers and markschemes in this thread: http://www.thestudentroom.co.uk/show...9&postcount=10

    Ignore question 1 because we won't be tested from anything related to a source book.


    Rf values:

    Rf = distance travelled by SOLUTE / distance travelled by SOLVENT

    Measure from the baseline of the chromatography paper to the spots.

    And that's pretty much it.


    Gas Chromatography:

    Mobile phase: Unreactive gas, eg nitrogen
    Stationary phase: Viscous (thick) liquid, eg an oil

    1 - Unknown mixture injected into long tube coated on the inside with the STATIONARY PHASE.
    2 - Mixture moves along tube with MOBILE PHASE until it comes out at the other end. Substances distributed between the phases (like in paper and thin-layer chromatography, too).
    3 - The time it takes a chemical to travel through the tube is called the RETENTION TIME.
    4 - Retention time can be used to identify different chemicals since the retention time is unique.

    Chromatogram for gas chromatography is a graph.

    They look a bit like this if you are unfamiliar with them:



    Each peek on the graph represents a different chemical.

    Distance along the X axis is the retention time - this can be looked up to identify the unique chemical.

    The peak height on the graph shows how much of that chemical was in the sample.


    And thin layer chromatography is just like paper chromatography, but instead of paper being used as the stationary phase, a thin layer of solid is used instead. A good example is silica gel on a glass plate.

    Mobile phase is again a solvent, just like paper chromatography.

    And I think that is just about everything you need to know about chromatography!

    Hope I helped!
    Thank you so much! This really helped, my teacher is so bad I have to self teach myself everything :/ but you really helped! Good luck for tomorrow's paper, hope its nice! Do u know of any other past paper because our teacher only gave us the 'in context' papers
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    (Original post by JazzyT17)
    Thank you so much! This really helped, my teacher is so bad I have to self teach myself everything :/ but you really helped! Good luck for tomorrow's paper, hope its nice! Do u know of any other past paper because our teacher only gave us the 'in context' papers
    Pleased that I helped! Any other C7 (or P7) questions let me know - it's good revision for me too!

    Yeah my teacher wasn't that good, so a lot of my C7 is self-taught too.

    The 'in context' papers are the old spec ones, but as I said you can just ignore question 1 since that was the question that relied on having the source sheet and complete the rest of the paper because it is still relevant to C7.

    I posted a link in one of my earlier posts in this thread to where I uploaded the 2008, 09, 10 and 11 summer papers and mark schemes for C7 in another thread.

    Sadly A173/02 has only been sat once and OCR hasn't publically released this paper. Your teacher may still have it - I got the B7 June 2013 paper from my biology teacher and my physics teacher emailed me the markscheme for that B7 June 2013 paper AND also sent me the P7 2013 paper and markscheme - so if anybody wants that let me know and I will share!

    The closest thing you can get to what we'll be sitting tomorrow is the specimen paper which I think is quite a hard paper.
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    (Original post by JasonBrown2K14)
    Pleased that I helped! Any other C7 (or P7) questions let me know - it's good revision for me too!

    Yeah my teacher wasn't that good, so a lot of my C7 is self-taught too.

    The 'in context' papers are the old spec ones, but as I said you can just ignore question 1 since that was the question that relied on having the source sheet and complete the rest of the paper because it is still relevant to C7.

    I posted a link in one of my earlier posts in this thread to where I uploaded the 2008, 09, 10 and 11 summer papers and mark schemes for C7 in another thread.

    Sadly A173/02 has only been sat once and OCR hasn't publically released this paper. Your teacher may still have it - I got the B7 June 2013 paper from my biology teacher and my physics teacher emailed me the markscheme for that B7 June 2013 paper AND also sent me the P7 2013 paper and markscheme - so if anybody wants that let me know and I will share!

    The closest thing you can get to what we'll be sitting tomorrow is the specimen paper which I think is quite a hard paper.
    You can find the june 2013 peper on page 79
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    (Original post by lyricalvibe)
    You can find the june 2013 peper on page 79
    ?? Please elaborate!!
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    Hi I don't understand how you can compare reactions between acids to show one is weaker than the other it was in the specimen paper thanks


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    (Original post by JasonBrown2K14)
    ?? Please elaborate!!
    Some dude posted all the past papers for C7 on page 79 of this thread theirs also thr specimen paper on the ocr website which i think you can access

    It's not a hard paper so fingers crossed tomorrows the same
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    (Original post by Swag>education)
    Hi I don't understand how you can compare reactions between acids to show one is weaker than the other it was in the specimen paper thanks


    Posted from TSR Mobile
    Same here, someone please say how D:
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    (Original post by Swag>education)
    Hi I don't understand how you can compare reactions between acids to show one is weaker than the other it was in the specimen paper thanks


    Posted from TSR Mobile
    I don't fully understand the question andi haven't done the specimen yet but couldn't you just compare neutralisation reactions with the 2 acids and alkali, the more alkali needed to reach colour change and hence end point the stronger the acid as you needed more alkali to neutralize (provided the 2 acids are the same concentration and volume)
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    (Original post by lyricalvibe)
    I don't fully understand the question andi haven't done the specimen yet but couldn't you just compare neutralisation reactions with the 2 acids and alkali, the more alkali needed to reach colour change and hence end point the stronger the acid as you needed more alkali to neutralize (provided the 2 acids are the same concentration and volume)
    I thought that but if you do methanoic acid+ sodium hydroxide---> sodium methanoate+ water
    and the mark scheme asks for a balanced equation so how do we know the symbol for sodium methanoate?
    Is it NaHCOOH ?:s


    Also this may sound like a silly question but does anyone have any tips on how to balance hard equations, like the ones that have 13s and that in them. It takes me forever and it wStes so much time!
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    (Original post by lyricalvibe)
    Some dude posted all the past papers for C7 on page 79 of this thread theirs also thr specimen paper on the ocr website which i think you can access

    It's not a hard paper so fingers crossed tomorrows the same
    Cheers for that! That guy rules.

    I'm going to print off the paper and do it tomorrow rather than the specimen. Also got a 2010 one (minus Q1) sitting on my desk.

    If I complete those two tomorrow morning then I will have done 4 past papers in preparation for this exam which is enough.

    To save people the time and hassle of trying to look for that post, here's the C7 June 2013 + Markscheme and P7 June 2013 + Markscheme and two C7 New Spec Specimens + Markschemes (and yes, the 2011 specimen is an A173 paper similar to the A173/02 paper we'll be sitting tomorrow) and a P7 New Spec Specimen + Markscheme.

    Happy revision!
    Attached Images
  1. File Type: pdf C7 June 2013 Markscheme.pdf (274.2 KB, 85 views)
  2. File Type: pdf C7 June 2013.pdf (260.7 KB, 75 views)
  3. File Type: pdf C7 New Spec Spcimen + Markscheme.pdf (296.6 KB, 118 views)
  4. File Type: pdf C7 New Spec Specimen Paper (2011) + Markscheme.pdf (538.4 KB, 96 views)
  5. File Type: pdf P7 June 2013 Markscheme.pdf (437.1 KB, 80 views)
  6. File Type: pdf P7 June 2013 [New Spec].pdf (138.5 KB, 88 views)
  7. File Type: pdf P7 New Spec Specimen + Markscheme.pdf (629.6 KB, 111 views)
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    If you want C7 legacy spec papers you can check my post here: http://www.thestudentroom.co.uk/show...9&postcount=10

    If you want P7 legacy spec papers - look no further.

    Simply ignore question 1 since it's not relevant to us and do the rest of the paper (hence why I haven't uploaded the inserts). It's all relevant to what we've learned in class.
    Attached Images
  8. File Type: pdf Physics June 2008 Series Markscheme (Incl. P7).pdf (750.8 KB, 86 views)
  9. File Type: pdf Physics P7 June 2008.pdf (155.6 KB, 77 views)
  10. File Type: pdf Physics P7 June 2010 Markscheme.pdf (161.7 KB, 116 views)
  11. File Type: pdf Physics P7 June 2010.pdf (138.4 KB, 72 views)
  12. File Type: pdf Physics P7 June 2011 Markscheme.pdf (126.6 KB, 82 views)
  13. File Type: pdf Physics P7 June 2011.pdf (162.7 KB, 86 views)
 
 
 

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