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    (Original post by shiney101)
    Can someone help me with q9? It's about percentage error, and they've said in the answer that the titre will be 24.4 so you can use that.
    I've forgotten what the formulae for percentage error is ://
    http://filestore.aqa.org.uk/subjects...T-P10-TEST.PDF

    Thanks

    (error/titre) X 100

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    If anyone can be arsed...Is it possible to run me through why there is a 3:5 ratio of manganate(VII): Iron(II) ethanedioate as opposed to the 2:5 ratio that I managed to get after cancelling out the electrons etc on June 2012 6(d)(i) ? I managed to get 4/5 for working through with my ratio but am a bit irritated at not being able to work out the right ratio.
    http://filestore.aqa.org.uk/subjects...5-QP-JUN12.PDF
    Ta
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    For enthalpy questions, in the mark scheme it shows that one mark is awarded for saying "∆H = Σ(enthalpies formation products) – Σ(enthalpies formation reactants)" etc... if you were to get the correct answer, would that score all the marks or is it required to state, like above what formula you are using? Just wondering because I always seem to get the correct answer for Born-Haber cycle questions but never write it out in words, for example the june 2015 mark scheme for question 1C.) says: "–∆Hf(MgCl2) + ∆Ha(Mg) + 1st IE(Mg) + 2nd IE(Mg) +2∆Ha(Cl)= –2EA(Cl) – LE(MgCl2)" Would I need to write this out even if I got the correct answer to score full marks?

    Hope that makes sense!!
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    (Original post by Hattie28)
    For enthalpy questions, in the mark scheme it shows that one mark is awarded for saying "∆H = Σ(enthalpies formation products) – Σ(enthalpies formation reactants)" etc... if you were to get the correct answer, would that score all the marks or is it required to state, like above what formula you are using? Just wondering because I always seem to get the correct answer for Born-Haber cycle questions but never write it out in words, for example the june 2015 mark scheme for question 1C.) says: "–∆Hf(MgCl2) + ∆Ha(Mg) + 1st IE(Mg) + 2nd IE(Mg) +2∆Ha(Cl)= –2EA(Cl) – LE(MgCl2)" Would I need to write this out even if I got the correct answer to score full marks?

    Hope that makes sense!!
    Is there anything in the margin saying things along the line or "or correct cycle"?
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    (Original post by Rabadon)
    Is there anything in the margin saying things along the line or "or correct cycle"?
    For this specific question, the born haber cycle was already done, I just had to work out one of the missing values, In the margin it says "Allow Enthalpy of Formation = sum of other enthalpychanges (incl lattice formation)" instead of saying "–∆Hf(MgCl2) + ∆Ha(Mg) + 1st IE(Mg) + 2nd IE(Mg) +2∆Ha(Cl)= –2EA(Cl) – LE(MgCl2)" I guess they may just one you to write it down so they can see what you're doing with all the values maybe?? To be on the safe side I may just start including the little formula bit before, just incase the correct answer alone doesn't get full marks.
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    (Original post by Hattie28)
    For this specific question, the born haber cycle was already done, I just had to work out one of the missing values, In the margin it says "Allow Enthalpy of Formation = sum of other enthalpychanges (incl lattice formation)" instead of saying "–∆Hf(MgCl2) + ∆Ha(Mg) + 1st IE(Mg) + 2nd IE(Mg) +2∆Ha(Cl)= –2EA(Cl) – LE(MgCl2)" I guess they may just one you to write it down so they can see what you're doing with all the values maybe?? To be on the safe side I may just start including the little formula bit before, just incase the correct answer alone doesn't get full marks.
    so how would you normally do it? Just follow the cycle and put the numbers in ur calculator as you go along? If you do that, just write out the numbers as u type them and I think that'll be fine.
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    Hi guys I need to attain a grade C and tbh that's all I want as I do struggle with chemistry but enjoy learning it hence why I took it but im not good at exams. What tips do you have so I can get my C im struggling with unit 5.
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    (Original post by lifegoals)
    Hi guys I need to attain a grade C and tbh that's all I want as I do struggle with chemistry but enjoy learning it hence why I took it but im not good at exams. What tips do you have so I can get my C im struggling with unit 5.
    How are you with unit 4? Most of unit 5 is a lot of memory so start off by learning all the equations you need to know and the colours. It's effort but it will get you a lot of marks. Doing past papers and understanding how the examiners want you to answer questions will help you attain marks. You can say the right thing but if it ain't on the mark scheme you wont get any marks.

    Unit 5 is generally lower grade boundaries than unit 4
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    (Original post by lifegoals)
    Hi guys I need to attain a grade C and tbh that's all I want as I do struggle with chemistry but enjoy learning it hence why I took it but im not good at exams. What tips do you have so I can get my C im struggling with unit 5.
    My advice would be use the spec as a checklist, once your fully confident on the topic go on to the next topic.
    Make notes based on your understanding and then check your notes with the textbook..
    Do the past papers, and don't just do them once do them multiple times you'll see progress

    Unit 5- in my opinion is quite knowledge-based take your time out to learn the colours/equations and try as hard as you can im sure you'll get what you want!
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    Can someone please help me work out the splitting pattern for 2,3 dichlorobutane?

    It says that it should be one quartet and one doublet...Can someone please explain this.
    I understand that there will only be two splitting patterns since there are only two different environments, but I don't get how to work out the patterns.

    Thanks
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    (Original post by shiney101)
    Can someone please help me work out the splitting pattern for 2,3 dichlorobutane?

    It says that it should be one quartet and one doublet...Can someone please explain this.
    I understand that there will only be two splitting patterns since there are only two different environments, but I don't get how to work out the patterns.

    Thanks
    Draw out the molecule first, I find that always makes it easier.

    It's a 4 carbon chain and the two middle carbons both have 1 chlorine and 1 hydrogen attached. This gives the first environment as they are also both attached to 1 methyl group. The splitting pattern is a qaurtet as for both hydrogens, they are attached to a carbon that is adjacent to a carbon with 3 hydrogens (3+1 if you follow the N+1 rule).

    The second environment is for both the methyl groups being attached to a carbon that has 1 chlorine and 1 hydrogen attached. The splitting pattern is a doublet as the hydrogens in both methyl groups are attached to a carbon that is adjacent to a carbon with only 1 hydrogen attached (1+1 as per N+1).

    Hopefully that helps somewhat
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    (Original post by smozsolution)
    Draw out the molecule first, I find that always makes it easier.

    It's a 4 carbon chain and the two middle carbons both have 1 chlorine and 1 hydrogen attached. This gives the first environment as they are also both attached to 1 methyl group. The splitting pattern is a qaurtet as for both hydrogens, they are attached to a carbon that is adjacent to a carbon with 3 hydrogens (3+1 if you follow the N+1 rule).

    The second environment is for both the methyl groups being attached to a carbon that has 1 chlorine and 1 hydrogen attached. The splitting pattern is a doublet as the hydrogens in both methyl groups are attached to a carbon that is adjacent to a carbon with only 1 hydrogen attached (1+1 as per N+1).

    Hopefully that helps somewhat
    So the hydrogens in the middle, even though there are two separate ones since they are have the same environment do you just consider them as 1 c-h group when figuring out the splitting pattern and the same with the ch3 group since they are both the same environment it's actually like one ch3 group?
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    (Original post by shiney101)
    So the hydrogens in the middle, even though there are two separate ones since they are have the same environment do you just consider them as 1 c-h group when figuring out the splitting pattern and the same with the ch3 group since they are both the same environment it's actually like one ch3 group?
    Yes they are two separate hydrogen atoms because they're both bonded to a carbon. They're considered to be part of one environment as they are exactly the same.

    If you think about it in terms of the integration ratio, it would be 2:6. There's still only 2 environments, one with the CH and the R group and one with the CH3 and the R group but this allows you to work out how many hydrogens are in each environment.

    I'm not really sure what you're trying to ask but I've tried to break it down for you from my understanding. If I've got it muddled then I'm sorry (and anyone else feel free to correct me). If you're still struggling try Chemrevise or a YouTube video on the topic.
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    Why does aluminium oxide have a lower melting point than magnesium oxide but a higher melting point than sodium oxide?
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    (Original post by JacobFinney)
    If anyone can be arsed...Is it possible to run me through why there is a 3:5 ratio of manganate(VII): Iron(II) ethanedioate as opposed to the 2:5 ratio that I managed to get after cancelling out the electrons etc on June 2012 6(d)(i) ? I managed to get 4/5 for working through with my ratio but am a bit irritated at not being able to work out the right ratio.
    http://filestore.aqa.org.uk/subjects...5-QP-JUN12.PDF
    Ta
    So sorry you've not had a reply regarding this! do you still need help?
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    (Original post by shiney101)
    Why does aluminium oxide have a lower melting point than magnesium oxide but a higher melting point than sodium oxide?
    Aluminium oxide has a +3 charge and oxide has a -2 charge (uneven balance of charges) therefore a higher charge means aluminium is more polarising and withdraws electron density from the oxide ion.
    This means that aluminium oxide has a slight covalent character- so a lower mp

    Note: I'm not too sure on the second part of the question if I figure it out ill let you know!
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    you know when they ask you to draw the repeating unit of a poly(alkene). does the monomer need to have brackets at the end ??
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    (Original post by Lilly1234567890)
    you know when they ask you to draw the repeating unit of a poly(alkene). does the monomer need to have brackets at the end ??
    no just include the trailing bonds
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    Can someone explain why (e)(ii) has the answer (R)OCH3?
    When using the integration information from the first part, we identified that there are six hydrogens (two methyl groups) at delta = 3.3. Can anyone explain why the answer is (R)OCH3 for (ii), as there is only one methyl group attached here!
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    (Original post by Louiseelg0rt)
    Can someone explain why (e)(ii) has the answer (R)OCH3?
    When using the integration information from the first part, we identified that there are six hydrogens (two methyl groups) at delta = 3.3. Can anyone explain why the answer is (R)OCH3 for (ii), as there is only one methyl group attached here!
    What paper is this from?
 
 
 
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