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OCR A2 CHEMISTRY F324 and F325- 14th and 22nd June 2016- OFFICIAL THREAD watch

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    (Original post by AqsaMx)
    Attachment 529211

    Why does the equation here have to involve OH- ions??
    The CO2 that is bubbled reacts with the water, H2O, that is on the left of the equilibrium equation, to form carbonic acid, H2CO3,

    which dissociates to form H+ and HCO3-,

    the H+ reacts with OH- on the right of the equilibrium equation, to form H2O,

    So the position of equilibrium shifts to the right to replace the OH-,

    sorry if this was already answered or didn't make sense
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    (Original post by mechanism)
    Can't polyamides be made from a carboxylic acid and an amine? Whereas polypeptides are made from lots of amino acids specifically, not lots of carboxylic acids and amines.
    Yep
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    2015 f321 f322 papers anyone ???


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    Can someone please explain how to construct the redox equation June 2014 Q8? Strugglingggggg
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    (Original post by zirak46)
    In weak acids, eq lies more to left due to PARTIAL dissociation.

    If not everything dissociated (partial), then obvs equilibirium will be more to left

    Get me?
    I get that they partially dissociate as the release of protons isn't complete but I don't get why it shifts to the left? why not the middle or the right?
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    (Original post by Kamara7)
    Yep
    yes but u can also make amide bonds with amino acids according to the book thats why im confused


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    Wait wait

    Is it because the ions will react together to form the reactants anyway? Therefore the position of equilibrium lies to the left?

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    (Original post by Hunnybeebee)
    Anyone got tips on how to do and answer nmr questions? (Ocr)

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    Start from the left to get the more 'important' peaks, and explain the splitting pattern of each (e.g. quartet=3 hydrogens on adjacent carbon) and try to link to hydrogen environment using the data sheet. You'll get quite a few marks from this even if you can't get the structure
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    (Original post by itsConnor_)
    Start from the left to get the more 'important' peaks, and explain the splitting pattern of each (e.g. quartet=3 hydrogens on adjacent carbon) and try to link to hydrogen environment using the data sheet. You'll get quite a few marks from this even if you can't get the structure
    I don't have a data sheet with me rn but say at 7ppm there's three different types of potential environments, which one do you select? Especially if the question hasn't hinted anything like it's an ester and you only have the spec to work from?

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    (Original post by ranz)
    yes but u can also make amide bonds with amino acids according to the book thats why im confused


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    an amide link is just the bond between an amine group, -NH2, and the carboxylic acid -COOH. So both polypeptides and polyamides have amide links, they are just formed in different ways.
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    (Original post by mechanism)
    an amide link is just the bond between an amine group, -NH2, and the carboxylic acid -COOH. So both polypeptides and polyamides have amide links, they are just formed in different ways.
    but theyre both formed by condesation reaction isnt it?


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    (Original post by Hunnybeebee)
    I don't have a data sheet with me rn but say at 7ppm there's three different types of potential environments, which one do you select? Especially if the question hasn't hinted anything like it's an ester and you only have the spec to work from?

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    If you are unsure about the group, try writing all the information about every other peak, and then see what is remaining. It's a process of elimination in some way. See if that works out for you
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    (Original post by Hunnybeebee)
    Wait wait

    Is it because the ions will react together to form the reactants anyway? Therefore the position of equilibrium lies to the left?

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    YOU KNOW THIS

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    (Original post by zirak46)
    YOU KNOW THIS

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    Oh my I'm crying tears of joy lmao

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    Hello peeps,
    In this question, why do I have to times the [OH-] by two??

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    (Original post by zirak46)
    Hello peeps,
    In this question, why do I have to times the [OH-] by two??

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    There are two moles of OH- dissociated per mole of Ca(OH)2

    Ca(OH)2 ---> Ca^2+ + 2OH-
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    (Original post by ReeceM1)
    There are two moles of OH- dissociated per mole of Ca(OH)2

    Ca(OH)2 ---> Ca^2+ + 2OH-

    Whaaaaat, i never knew that was a rule.

    Is that the same if its h2so4? Meaning theres two moles of H?
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    (Original post by zirak46)
    Whaaaaat, i never knew that was a rule.

    Is that the same if its h2so4? Meaning theres two moles of H?
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    It will always tell you in the question how many moles of H+ will dissociate in H2SO4,
    But normally only 1 H+ does and with our spec I've only ever seen pH questions with monobasic acids.
    In reality the first proton dissociates but the HSO4^- that remains actually acts as a weak acid:

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    (Original post by ReeceM1)
    It will always tell you in the question how many moles of H+ will dissociate in H2SO4,
    But normally only 1 H+ does and with our spec I've only ever seen pH questions with monobasic acids.
    In reality the first proton dissociates but the HSO4^- that remains actually acts as a weak acid:

    Ahhh nice but if theres ever Mg (OH)2 then itll be 2 moles of OH- ions?
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    (Original post by zirak46)
    Ahhh nice but if theres ever Mg (OH)2 then itll be 2 moles of OH- ions?
    Yepp
 
 
 
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