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    (Original post by Dolphino)
    Hey guys, do we need to know about the contact process in detail? Also what about the producing urea stuff in the hsw section??????
    You don't really need to know much, just remember the equation:
    2SO2 + O2 <----> 2SO3

    You'll just need to know that it's exothermic, from there you can figure out what will happen with changes of pressure. They're all gaseous state, so again from here you can predict what will happen when pressure is changed.

    The only real thing you'd need to remember is definitely the part where they talk about atom economy & recycling any unreacted reagents.

    To answer your second question, I've never seen anything to do with urea
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    (Original post by posthumus)

    To answer your second question, I've never seen anything to do with urea
    I think he's referring to something in the A2 chemistry student book ( by Ann Fullick)
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    Thanks guys, and yeah I was talking about the Ann fullick book.
    Just another question: with acyl chlorides plus ethanol to make ester, would u call it nucleophilic substitution, condensation or nucleophilic addition/elimination. Every book says something different!
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    (Original post by Dolphino)
    Thanks guys, and yeah I was talking about the Ann fullick book.
    Just another question: with acyl chlorides plus ethanol to make ester, would u call it nucleophilic substitution, condensation or nucleophilic addition/elimination. Every book says something different!
    It should be condensation as HCl is being produced. :P

    I have a question!
    For Q8 Jan 13 where we had to chose a best indicators with only the values of concentration of NaOH given, without a titration curve, how would we know which one to choose? (Qs was strong base + weak acid, ans was C)

    I tried the George Facer txtbook's "the rule of two"
    it doesnt seems to work in deducing the indicators needed for strong acid + strong base
    (indicator was apparaently thymophalein with range 8.0 - 9.6, if i remembered correctly)
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    (Original post by Dolphino)
    Thanks guys, and yeah I was talking about the Ann fullick book.
    Just another question: with acyl chlorides plus ethanol to make ester, would u call it nucleophilic substitution, condensation or nucleophilic addition/elimination. Every book says something different!
    Sounds like addition elimination... as HCl is eliminated. Or I think it can be called esterification too



    (Original post by StellaRawr11)
    It should be condensation as HCl is being produced. :P

    I have a question!
    For Q8 Jan 13 where we had to chose a best indicators with only the values of concentration of NaOH given, without a titration curve, how would we know which one to choose? (Qs was strong base + weak acid, ans was C)

    I tried the George Facer txtbook's "the rule of two"
    it doesnt seems to work in deducing the indicators needed for strong acid + strong base
    (indicator was apparaently thymophalein with range 8.0 - 9.6, if i remembered correctly)
    Doesn't it ? :confused: The rule of two give pH 9 ... which seems to be within that range of 8-9.6

    Also does anyone know where I can get the actual data booklet from? (pink one I believe). In January the one given in our exam was very different to the ones we usually used, and so much time was wasted on particular question when I couldn't find the standard entropy of a compound

    Thanks
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    (Original post by posthumus)
    Sounds like addition elimination... as HCl is eliminated. Or I think it can be called esterification too





    Doesn't it ? :confused: The rule of two give pH 9 ... which seems to be within that range of 8-9.6

    Also does anyone know where I can get the actual data booklet from? (pink one I believe). In January the one given in our exam was very different to the ones we usually used, and so much time was wasted on particular question when I couldn't find the standard entropy of a compound

    Thanks
    How? Could u explain please?
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    (Original post by StellaRawr11)
    How? Could u explain please?
    Strong Base - weak acid, rule of 2... tells you to add 2 to 7 (pH will increase due to strong base)

    so it's 9

    for strong acid, weak base... it would have been 7-2 = 5
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    (Original post by SKK94)
    LOL is that a physics question?
    I think:
    1) Nuclear fusion gives rise to the elements (that our bodies consist of)
    2) Nuclear fusion occurs in supernovae (where there is enough energy/heat to produce the heavy elements such as iron etc)
    (a supernova is the one of the possible last stages in stellar evolution, so it consists of material that the star was made of - i.e startdust?)

    Here's the physics unit 5 thread for edexcel (if that is what you're doing)
    http://www.thestudentroom.co.uk/show...2293091&page=4
    Thanks anyways its chemistry but I think the answers could be similar do u have any links for chemistry? That could help me😃😜


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    (Original post by 1Dswag)
    Thanks anyways its chemistry but I think the answers could be similar do u have any links for chemistry? That could help me


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    Which exam board are you doing? You mean links to a chemistry thread?
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    (Original post by SKK94)
    Which exam board are you doing? You mean links to a chemistry thread?
    OCR exam board & yes links to a chemistry thread!


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    (Original post by 1Dswag)
    OCR exam board & yes links to a chemistry thread!


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    Oh ok.
    These are a few I found
    http://www.thestudentroom.co.uk/show...chemistry+2013
    http://www.thestudentroom.co.uk/show...3#post43040728
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    Omg thank you that's really good help.😜😃😉


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    Hey guys I have another question. How is the entropy of system affected by temperature? Would you say it's affected as particles have more energy therefore more disorder or would you say that only entropy of surroundings is affected by temp, not the system.

    Thanks
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    (Original post by Dolphino)
    Hey guys I have another question. How is the entropy of system affected by temperature? Would you say it's affected as particles have more energy therefore more disorder or would you say that only entropy of surroundings is affected by temp, not the system.

    Thanks
    You don't need to know much about this, but I'll tell you what typically happens:

    If a reaction is exothermic then kinetic energy is transferred to the surroundings. The surrounding becomes more disordered (hence entropy increase as Ssurrounding is positive)... but the entropy of system usually has the opposite effect, since the system has lost energy, the particles have lower kinetic energy... therefore they are more ordered And usually entropy of system is therefore negative.

    The opposite applies if the reaction is endothermic
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    Thanks. I was actually wondering whether an increase/decrease in temp would have an effect on the entropy of system.


    I have a second qu, does the ph of water remain neutral at all temp? I've just seen a qu which says that at higher temp the ph of water is lower. I don't understand this as the ionisation of water shows a 1:1 ratio for hydrogen and hydroxide ions? Explain pls :")
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    (Original post by Dolphino)
    Thanks. I was actually wondering whether an increase/decrease in temp would have an effect on the entropy of system.


    I have a second qu, does the ph of water remain neutral at all temp? I've just seen a qu which says that at higher temp the ph of water is lower. I don't understand this as the ionisation of water shows a 1:1 ratio for hydrogen and hydroxide ions? Explain pls :")
    Aah good question, it confuses me too... but I wouldn't dwell on it too much. Yes the pH is lower but that does not mean it is acidic, it's in fact neutral... as you said there's a 1:1 ratio and there will be same amount of OH- & H+ as equilibrium shifts to the right

    However since the temperature has changed and the ionisation of water is endothermic the Ka value is also increases... overall everything increases.

    When we do calculations we assume also that the ionic product of water is 1x10^-14 (being carried out at room temperature) That's why it can seem odd that something is neutral yet has a pH below 7... this is because it's not being done at room temperature anymore.
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    Thanks posthumus- good luck with ur revision btw and hopefully you will ace the chem on Wednesday!!!
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    (Original post by Dolphino)
    Thanks posthumus- good luck with ur revision btw and hopefully you will ace the chem on Wednesday!!!
    Your welcome & you too! I really do need to, chemistry is not my subject ... and I've done spectacularly bad in the exams so far !
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    (Original post by posthumus)
    Your welcome & you too! I really do need to, chemistry is not my subject ... and I've done spectacularly bad in the exams so far !
    What do you mean chemistry is not ur subject? Ur awesome at it. You probably just need to sort out ur exam technique as u seem to have the knowledge! Which exams have u had so far? I'm sure you've done better than you think
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    (Original post by Dolphino)
    What do you mean chemistry is not ur subject? Ur awesome at it. You probably just need to sort out ur exam technique as u seem to have the knowledge! Which exams have u had so far? I'm sure you've done better than you think
    I do understand it but only because this like the only subject I study at home, but yh I just don't understand exam questions sometimes.... I dunno, like I was getting A*s in some of my past papers for unit 4 before Jan exam. I completely blanked out and got a D Also the data booklet was real issue for me, do you get the pink one? If so where can I get it from

    The exams I've done so far: M1,D1,C2... PHYA1, PHYA2... Chem1, Chem2... and I have another 6 more to go

    I hope I have, though I think I need to get atleast 170 UMS across both unit 4 & 5 to get my B grade. Thanks for the encouragement, how has your exams been so far ?
 
 
 
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