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Edexcel A2 Chemistry Exams -6CH04 (14th June) and 6CH05 (22nd June) Discussion Thread Watch

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    (Original post by ST_123)
    Thanks i did the question now. Although i still don't quite understand how finding the mol of hcl and naoh and subtracting the two gives me the mol left in equilibrium of ethanoic acid.
    The thing is that HCl here acts as the catalyst in this reaction but because HCl is a strong acid than ethanoic acid, it also reacts with NaOH. Now, with NaOH and HCl reacting, we know they have a 1:1 ratio(For HCl and NaOH as well as for CH3COOH) but you see, the base has around 0.045 moles and HCl is 0.005 moles which have reacted so this means that the rest of the acid remaining here is CH3COOH.
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    Could someone please explain how you could deduce the second half equation without knowing it? Really appreciate your help

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    (Original post by Funky_Giraffe)
    Could someone please explain how you could deduce the second half equation without knowing it? Really appreciate your help

    From as, what 2 possible products are there if i oxidise a primary alcohol?
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    (Original post by samb1234)
    From as, what 2 possible products are there if i oxidise a primary alcohol?
    aldehyde or carboxylic
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    (Original post by sabahshahed294)
    The thing is that HCl here acts as the catalyst in this reaction but because HCl is a strong acid than ethanoic acid, it also reacts with NaOH. Now, with NaOH and HCl reacting, we know they have a 1:1 ratio(For HCl and NaOH as well as for CH3COOH) but you see, the base has around 0.045 moles and HCl is 0.005 moles which have reacted so this means that the rest of the acid remaining here is CH3COOH.
    Ah ok that makes sense now. Thanks a lot!
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    how is everyone revising for Chemistry sorry if its a stupid question:blush:
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    (Original post by mizzyportia)
    how is everyone revising for Chemistry sorry if its a stupid question:blush:
    Going through notes because I keep on forgetting stuff from it tbh lol :P
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    (Original post by ST_123)
    Ah ok that makes sense now. Thanks a lot!
    You're welcome
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    (Original post by mizzyportia)
    how is everyone revising for Chemistry sorry if its a stupid question:blush:
    Made a lot of detailed notes and then will do a lot of past papers probably
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    Hey, does someone mind explaining exactly why C is the correct answer here? I put A :/

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    (Original post by Funky_Giraffe)
    Hey, does someone mind explaining exactly why C is the correct answer here? I put A :/

    What is the bronsted lowry definition of a base, and how is it relevant here
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    (Original post by samb1234)
    What is the bronsted lowry definition of a base, and how is it relevant here
    A base is a proton acceptor. Is it something to do with the inductive effect of the alkyl group in CH3NH2 which makes it more likely to accept a proton?
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    (Original post by Funky_Giraffe)
    A base is a proton acceptor. Is it something to do with the inductive effect of the alkyl group in CH3NH2 which makes it more likely to accept a proton?
    Essentially yes. We know from tertiary halognenoalkanes from as that part of the reason they react via sn1 is that methyl groups are slightly electron donating, reducing the magnitude of the +ve charge on the Carbon. The same thing happens here - the methyl group slightly increases the negativity of the nitrogen compared to just NH3. The C6H5NH2 is similar to phenol - the lone pair of the nitrogen is partially delocalised into the ring system making it less -ve and therefore it doesn't pick up a proton as easily
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    (Original post by samb1234)
    Essentially yes. We know from tertiary halognenoalkanes from as that part of the reason they react via sn1 is that methyl groups are slightly electron donating, reducing the magnitude of the +ve charge on the Carbon. The same thing happens here - the methyl group slightly increases the negativity of the nitrogen compared to just NH3. The C6H5NH2 is similar to phenol - the lone pair of the nitrogen is partially delocalised into the ring system making it less -ve and therefore it doesn't pick up a proton as easily
    Thanks!!
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    Name:  Screenshot_2016-05-24-15-18-52.png
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Size:  120.6 KBI am currently stuck on question 5 of the photo. I was hoping someone could help. The answers C but i cant work out why. Thanks in advance.
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    https://c838cff4741acb48ae1ed62e5992...0Chemistry.pdf

    For 18ai) im confused as to how to find the order of Br-. Hoping someone could explain it. Thanks
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    (Original post by ayvaak)
    Name:  Screenshot_2016-05-24-15-18-52.png
Views: 307
Size:  120.6 KBI am currently stuck on question 5 of the photo. I was hoping someone could help. The answers C but i cant work out why. Thanks in advance.
    The systematic, logical way of going through this would to recognise that transition metals have an electronic structure of the form [Ar] 3dx 4sy . Working from Ti to Cu on the periodic table, you've got

    Ti - [Ar] 3d1 4s2
    V - [Ar] 3d2 4s2
    Cr - [Ar] 3d3 4s2
    Mn - [Ar] 3d5 4s1

    ...and so on

    Now, the thing you should note is that the difference in energy between the 4s- and 3d- sub-shells is minimal. Therefore, you should not expect a big jump between the last electron being removed from the 4s and the first from the 3d (electrons are removed from the 4s before the 3d)

    So, you should be thinking all of this when you see the question, and bearing it all in mind, study the options. If this were a transition metal you would only get a jump between the 3rd and 4th ionisation energies onwards, because that's when the first Transition Metal, Titanium, loses it's first electron that's in neither the 3d nor 4s sub-shell (see the electronic structure of Ti above), so it's the first opportunity for a big jump in ionisation energy. So disregard options A and B immediately because their big 'jump' is before the 3rd and 4th ionisation energies. Notice how option D doesn't seem to have any jumps between the ionisation energies. So by default the answer is C.
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    How many Unit 4 and Unit 5 past papers have people managed to track down? (Im trying to find out if Im missing any) There seems to be quite a few with the addition of international and january papers
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    (Original post by ayvaak)
    How many Unit 4 and Unit 5 past papers have people managed to track down? (Im trying to find out if Im missing any) There seems to be quite a few with the addition of international and january papers
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    (Original post by samb1234)
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    You sound well prepared for Chemistry!
 
 
 
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