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OCR AS - Chemistry Unit F322 - Chains, energy and resource - REVISION! watch

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    (Original post by Phenylethylamine_)
    Ahh okay, because in theofficial/course textbook, on the first page of 2.2 for the hydration of ethene, it says 60atm?
    Yep I can visualize the page I have read it that many times, and was very reluctant to change the atm from 60 to 100. I have seen it in maybe 3 past papers, the lower limit of whose answers were all over 60. The upper limit has been 400
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    (Original post by supersping)
    heyy need help!

    how do you work out enthalpy change of formation when you are giving combustion data?
    "If you are given enthalpy of formation (to calculate enathlpy change of reaction or combustion) you would have to reverse the arrows of a enthalpy cycle for the reactants.

    So its sum of enthalpy change of formation of products take way sum of enthalpy change of formations of reactants.

    And if you are given enthalpy change of combustion then you would have to do the opposite, look at the examiner tip boxes on pages 199 and 201 of the course book as it summarises it using notation that I cannot/do not know how to type out on a forum.

    Oh, and if you are calculating enthalpy change of reaction, then it is associated with the molar quantities in the equation- you may have to multiply out your answer if it is calculated for one mole of a substance that does not appear as one mole in the equation."
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    Would be really gud if someone list defi that might come up in the exam ! we did it for F321 and one of em came up today !!
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    homologous series: organic compunds having same functional group, differing by ch2
    functional group: determines chemical reaction of a compund
    homolytic: two radicals
    heterolytic: one cation one anion
    atom economy: Mr of desired products/Mr of all productsx100
    radical:species with unpaired electron
    electrophile: attracted to electrons (it likess electrons)
    nucleophile: attracted to electron deficiency, donatessss electron pair

    standard conditions: 101kPa, 298K and 1Molar
    enthalpy change of;
    formation: one mole of a substance is formed from its elements in their natural state under standard conditions
    combustion: one mole of a substance burns completely in sufficient oxygen supply under standard condition
    average bond enthalpy: ????? someone provide a decent definition! i have a feeling it will come up!!

    la chateliers principle:if a chemical system at equilibrium experiences a change in temp,partial pressure, conc or volume, then the system will move to counteract the change




    anddd thats all of the ones i think they might ask lol, i kno i have missed out some important ones, eg stereoisomer but theyre easier than these

    p.s. dont frget to find average bond enthalpy, its gonne be theree im tellling u!!


    good luck everyone!
    ok so now can someone explain to me the green chemistry rubbish! what principles should we kno?
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    Guys how often does enthalpy come up? And is it hard to revise? I'm devoting 1/2 my day to master enthalpy, can it be done?

    It seems the same as the moles questions; just learning how to do it and applying it over and over again in different contexts.
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    (Original post by YingYang)
    Guys how often does enthalpy come up? And is it hard to revise? I'm devoting 1/2 my day to master enthalpy, can it be done?

    It seems the same as the moles questions; just learning how to do it and applying it over and over again in different contexts.
    Yeah it's pretty easy.

    Also - make sure you know the green chemistry module inside out.
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    Petroleum

    CRUDE OIL - AKA PETROLEUM

    • Fractional Distillation


    1. CRUDE OIL VAPORISED AT 350C
    2. Vaporised crude oil placed in Fractionating Column
    3. Rises up through the trays
    4. Largest hydrocarbons DON'T VAPORISE due to too high BOILING POINTS
    5. so fall to bottom of chamber forming GOOEY RESIDUE
    6. As crude oil vapour goes up the column, it gets COOLER.
    7. Due to differences in chain lengths, each fraction CONDENSES at different temperatures.
    8. Fractions drawn off at different levels
    8. Hydrocarbons with LOWEST BOILING POINTS DON'T CONDENSE. They're drawn off as gases at TOP of column.
    Most fractions are either used as FUELS or to make PETROCHEMICALS,.
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    Definitions:

    PETROCHEMICAL = any compound made FROM CRUDE OIL but is NOT A FUEL.

    CRACKING = Breaking long-chain hydrocarbons into SMALLER hydrocarbons. Involves breaking C-C bonds.
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    (Original post by J DOT A)
    Yeah exactly the mistake I made, thus I am retaking this unit again!
    Just make sure your organic chemistry is good and your sorted. I have done A2 so this should be alot easier I am hoping
    I dont understand what is this how far how fast nonsense? what do you mean by application questions

    Please someone explain! <3
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    Give 2 ways of increasing sustainability if in your reaction you have an undesired product and the atom economy is low.
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    (Original post by J DOT A)
    Give 2 ways of increasing sustainability if in your reaction you have an undesired product and the atom economy is low.
    Find a use for the undesirable product

    use a catalyst to reduce activation energy needed
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    (Original post by YingYang)
    Guys how often does enthalpy come up? And is it hard to revise? I'm devoting 1/2 my day to master enthalpy, can it be done?

    It seems the same as the moles questions; just learning how to do it and applying it over and over again in different contexts.
    Enthalpy change is pretty much guaranteed to come up every year and it's pretty easy marks. The questions normally take you through it step by step anyway.
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    omg i still have so much to revise for and so less time, i have 2 exams by end of week and not even revised even a 1/3rd for each exam and i need A grades. cant stop panicking, feel so dumb and feel like i will got mental on results day if i dont get in2 uni, who else thinks they may feel like their life will b ova if they don't get into their chosen course? :headfire:
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    (Original post by tateco)
    Enthalpy change is pretty much guaranteed to come up every year and it's pretty easy marks. The questions normally take you through it step by step anyway.
    I had no idea you did ocr chemistry too :P

    How'd you do in unit 1?

    Also I am not liking having econ2 and f322 in same day :P (I also have OCR ICT same time as econ2 but I don't think many people have this)
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    (Original post by YingYang)
    I had no idea you did ocr chemistry too :P

    How'd you do in unit 1?

    Also I am not liking having econ2 and f322 in same day :P (I also have OCR ICT same time as econ2 but I don't think many people have this)
    Aha, yep :P

    I got 84/90 in unit 1 and 37/40 in practicals, you?

    You think that's bad, I have Biology and Maths on Thursday then two on Friday :| going to be hell.
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    (Original post by tateco)
    Aha, yep :P

    I got 84/90 in unit 1 and 37/40 in practicals, you?

    You think that's bad, I have Biology and Maths on Thursday then two on Friday :| going to be hell.
    Wow thats so good o.o

    I got 70/90 but missed the last page by accident (which was easy 5 marks)
    Had the retake yesterday, was so much harder than usual, I thought anyway. I now have confidence now in chemistry, hate OCR with a passion.

    Maths will be alright, biology... well good luck with that :P
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    (Original post by YingYang)
    Wow thats so good o.o

    I got 70/90 but missed the last page by accident (which was easy 5 marks)
    Had the retake yesterday, was so much harder than usual, I thought anyway. I now have confidence now in chemistry, hate OCR with a passion.

    Maths will be alright, biology... well good luck with that :P
    Ah, I remember the horror when they took the exams in and loads of people had missed the back page. Hopefully the grade boundaries will be low for you

    Maths is actually going to be the worst exam out of all of them because it's Stats, it's probably going to be the hardest of all of my exams!
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    (Original post by tateco)
    Ah, I remember the horror when they took the exams in and loads of people had missed the back page. Hopefully the grade boundaries will be low for you

    Maths is actually going to be the worst exam out of all of them because it's Stats, it's probably going to be the hardest of all of my exams!
    Tateco, do you have AQA Biology and OCR stats on thursday? I have those exams. And I'm not looking forward to stats either.
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    (Original post by Killjoy-)
    Tateco, do you have AQA Biology and OCR stats on thursday? I have those exams. And I'm not looking forward to stats either.
    OCR Biology but OCR stats yeah, it should be okay, I think I just expect too much of myself
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    anyone else done the june 2010 paper and found it really hard?
 
 
 
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