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OCR Salters Chemistry F335 12th June 2013 Exam revision thread Watch

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    (Original post by TheNote)
    I understand why it's Li2S i didn't understand why it couldn't be called dilithium sulphide
    Lithium is a metal, you never give those prefixes to metals, imagine di-gold

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    (Original post by ElChapo)
    Lithium is a metal, you never give those prefixes to metals, imagine di-gold

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    lol yeah sounds stupid...but in my head...it sounded right....
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    Would someone be able to post what functional groups/families undergo which type of reactions?
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    Electrophilic addition:

    • alkenes

    Electrophilic substitution:
    • arenes/benzene

    Nucleophilic addition:
    • aldehydes
    • ketones

    Nucleophilic substitution:
    • amines
    • halogenoalkanes
    • acyl chlorides

    Radical substitution:
    • halogenoalkanes


    is that all there is?
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    (Original post by nukethemaly)
    Electrophilic addition:

    • alkenes

    Electrophilic substitution:
    • arenes/benzene

    Nucleophilic addition:
    • aldehydes
    • ketones

    Nucleophilic substitution:
    • amines
    • halogenoalkanes
    • acyl chlorides

    Radical substitution:
    • halogenoalkanes


    is that all there is?
    God bless your soul
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    HOWWWWW IS pH of a buffer calculated?!

    Is it the ionisation product of water/[H+]?
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    (Original post by physicso)
    HOWWWWW IS pH of a buffer calculated?!

    Is it the ionisation product of water/[H+]?
    You should be given all the numbers you need:
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    Feb 2012 paper, Q4, iodine number... What even?!

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    (Original post by suncake)
    You should be given all the numbers you need:
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    Feb 2012 paper, Q4, iodine number... What even?!

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    Yeh but whats the actual formula?


    Yeah that was weird - i think you just had to use the fact that on c2+ i2 goes to c2i2 (saturated bonds)
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    (Original post by physicso)
    Yeh but whats the actual formula?


    Yeah that was weird - i think you just had to use the fact that on c2+ i2 goes to c2i2 (saturated bonds)
    The one I just attached a picture of...? Sorry if I'm misunderstanding you :')

    Aha yeah got it, it was the second part that confused me, but found the explanation on here so it's all good!

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    (Original post by physicso)
    Yeh but whats the actual formula?


    Yeah that was weird - i think you just had to use the fact that on c2+ i2 goes to c2i2 (saturated bonds)

    key

    HA : 'acid'
    A- N+ : 'salt of conjugate base'


    for the reaction

    HA <=> H+ A-

    equation (products over reactants)

    Ka = [H+][A-] / [HA]


    Assumptions:

    1. [HA] = [HA]eq

    2. [A-] = [H+ A-]
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    Can someone please explain to me how to do Q1 (d) (i) from June 12

    http://www.ocr.org.uk/Images/131296-...-by-design.pdf
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    Reagents and conditions of Amide formation from ethanol and ethanoyl chloride? Do you have to reflux or add acid or anything?
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    (Original post by Salmonidae)
    Reagents and conditions of Amide formation from ethanol and ethanoyl chloride? Do you have to reflux or add acid or anything?
    do you mean ethanoyl chloride + aminoethane? my revision guide doesn't give any specific conditions, just calls the process acylating
    at least i hope you mean that because i don't know how to make an amide using ethanol + ethanoyl chloride - unless you meant making an ester?
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    (Original post by Salmonidae)
    Reagents and conditions of Amide formation from ethanol and ethanoyl chloride? Do you have to reflux or add acid or anything?
    From ethanoyl chloride conc. ammonia at room temp
    not sure about from alcohol sorry
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    Can anyone explain solubility and insolubility in terms of intermolecular bonding please?
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    (Original post by Salmonidae)
    Reagents and conditions of Amide formation from ethanol and ethanoyl chloride? Do you have to reflux or add acid or anything?
    add NH3 at room temp, ethanol is used as a solvent.
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    (Original post by stealth_writer)
    Can someone please explain to me how to do Q1 (d) (i) from June 12

    http://www.ocr.org.uk/Images/131296-...-by-design.pdf
    heres how i did it,
    forumula used: Moles = Concentration x Vol
    (1 mol of gas occupies 24dm3)

    1. i worked out the moles of oxygen, 8.3 x 10-3 x 24 = 0.1992
    2. they told us ratio of nitrogen to oxygen is 4:1, therefore moles of nitrogen is 0.1992 x 4 = 0.7968.
    3. since we know the moles of nitrogen, we can work out its concentration using the formula: 0.7968 / 24 = 0.033
    Not sure why the mark scheme want it as 0.033 rather than 0.03 though
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    (Original post by stealth_writer)
    Can someone please explain to me how to do Q1 (d) (i) from June 12

    http://www.ocr.org.uk/Images/131296-...-by-design.pdf
    24 * 5

    So you finding the total volume of air.

    4:1 ratio of N2 to O2

    so 1/120 = 8.3*10^-3

    4/120 = 0.03
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    Can someone help me with Jan 13 Q's 3 (d) (i), Q4 (d) (v) please
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    (Original post by Mtheodore)
    heres how i did it,
    forumula used: Moles = Concentration x Vol
    (1 mol of gas occupies 24dm3)

    1. i worked out the moles of oxygen, 8.3 x 10-3 x 24 = 0.1992
    2. they told us ratio of nitrogen to oxygen is 4:1, therefore moles of nitrogen is 0.1992 x 4 = 0.7968.
    3. since we know the moles of nitrogen, we can work out its concentration using the formula: 0.7968 / 24 = 0.033
    Not sure why the mark scheme want it as 0.033 rather than 0.03 though
    part 1. I wouldn'tuse this as a valiud method all the time as while this mark scheme allows it, it doesn't always want you to use the "show that" part of the equation in your working out.
 
 
 
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