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Edexcel chemistry unit 5 - question & answer watch

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    but on the examiners report it says quote ' correct chemistry will never go unrewarded'..lucas' is correct so it shud be accepted
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    you are probably right :-)
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    btw i cant answa ure Q..its not on edexcel sylabus HEHE
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    good point.... oops.. and I have the syllabus in front of me.. stupid me... umm... here's another one.

    How can you deduce a reaction mechanism from kinetic data such as a rate equestion (now that IS edexcel... Topic 5.4 (f) :-)
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    I wouldn't test a ketone with iodoform, pentan-3-ol is a secondary alcohol but will not react with iodine and NaOH.

    To convert benzene to a phenol, I'd nitrate it by adding concentrated H2SO4 and HNO3, to form the nitronium ion in situ to make nitrobenzene. then reduce with tin and conc hydrochloric acid in reflux to make phenylamine, then substitute that with NaOH and ethanol?

    Or maybe, add dichloromethane with AlCl3 and benzene to make chloromethylbenzene, then substitute the chlorine by adding KOH?
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    (Original post by rieuwa)
    good point.... oops.. and I have the syllabus in front of me.. stupid me... umm... here's another one.

    How can you deduce a reaction mechanism from kinetic data such as a rate equestion (now that IS edexcel... Topic 5.4 (f) :-)
    the rate determining step will have reactants whose concentration is of power 1 or greater in the rate equation. powers of 2 indicate two moles of the species are required in the rate determining step. species not in the rate determining step and ones which do not appear in the rate equation.

    Q: What are the colours of vanadium ions in aqueous solution in oxidation states 5+, 4+ 3+ and 2+?
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    To convert benzene to a phenol, I'd nitrate it by adding concentrated H2SO4 and HNO3, to form the nitronium ion in situ to make nitrobenzene. then reduce with tin and conc hydrochloric acid in reflux to make phenylamine, then substitute that with NaOH and ethanol?

    even simpler.. I think... once you have phenylamine... add HNo2 at T>10deg (ok terrible yield.. but you've made phenol. :-) )

    Or maybe, add dichloromethane with AlCl3 and benzene to make chloromethylbenzene, then substitute the chlorine by adding KOH?
    Excuse me if I'm talking nonsense... but would that not give phenyl methanol and not phenol ? Hit me on the head If I'm talking nonsense
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    (Original post by mik1w)
    the rate determining step will have reactants whose concentration is of power 1 or greater in the rate equation. powers of 2 indicate two moles of the species are required in the rate determining step. species not in the rate determining step and ones which do not appear in the rate equation.

    Q: What are the colours of vanadium ions in aqueous solution in oxidation states 5+, 4+ 3+ and 2+?
    +5 (VO2+ ==> yellow
    +4 (VO2+) ==> blue
    +3 (V3+ ) ==>green
    +2 (V2+ ) ==> lavender / purple

    Here is a question I'm not sure of the answer: what would happen if you reduced benzoic acid (C6H5-COOH) with LiAlH4 in dry ether? would you get phenol do you think?
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    u wudnt get phenol..i think ud get C6H5CH3OH...i dnt think it can happen tho

    Q: give the ionic equation for the reaction between Iodine and sodiumthiosulfate
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    I(2) + 2S(2)O(3) -2 ---> 2I- + S(4)O(6) 2-

    suggest a nessecary condition during an experiment to obtain the rate of reaction to ensure accurate results. (a bit annoying but on the specimen paper)
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    (Original post by mik1w)
    I(2) + 2S(2)O(3) -2 ---> 2I- + S(4)O(6) 2-

    suggest a nessecary condition during an experiment to obtain the rate of reaction to ensure accurate results. (a bit annoying but on the specimen paper)
    standard conditions ? heat under reflux ?
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    constant temperature

    nessasary condtions for storage cells??
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    I don't know any..
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    Q: What are the experimental techniques for following a reaction?
    Conditions?

    This question came up quite a lot of times..... I can hardly get any mark....
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    well there are many different tequniques depending on the reaction.

    1. colourimetry, first calibrate colourimeter, put sample reacting in it and this will plot results. benefits - no need for sampling so accurate timing. required a coloured reagent or product

    2. sampling at time intervals for titration and analysis, eg. iodine with thiosulphate, or anything that manganate reduces. probloem - error in sampling and reaction may still proceed in sample

    3. pH meter in solution, to plot change in pH over time, can be used to find change in hydrogen ion concentration over time

    etc...

    define a d-block element (markscheme says something different to my defenition above):

    element whose change in electron configuration over previous element is an extra electon in the d-block. (does not accept "highest energy level electron in d-block)

    Q: why can the rate equation not be determined from the stoichiometric equation?
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    the rate equation is based upon the species in the rate determining step...the stoichiometric equition may contain species that enter the reaction outside the RDS...

    Describe the corrosion of Iron with equations
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    i dnt think u shud put pH meter down...its regarded as inaccurate and u only get 1 mark ..

    can sum1 do this Q please :tsr:
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    sum1 please do the Q
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    well the diagram would be really close to a straight line, nd th ereason for both having high boiling points would be the hydrogen bonding that they would have, the 2 methyl,propan,2ol would have an extra methyl group which would give the substance, just a little more stability.. Oh yea fractional distillation would be almost impossible as you distill to + or - 2 degrees pf literature value
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    hydrogen bonding would occur? I would have said that the slight increase in atomic mass (by 15) would increase the strength of the vdw forces - btw, what INTRA molecular forces can there be? Is zwitterion interaction an example of intramolecular forces?
 
 
 
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