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    (Original post by Super199)
    So the functional group isomer of butanoic acid would be butanone?
    No.

    Butanone: C4H8O
    Butanoic acid: C4H8O2

    The molecular formula is different.

    Propanal: C3H6O
    Propanone:C3H6O

    Propanoic acid: C3H6O2
    Methyl Ethanoate: C3H6O2


    http://www.chemguide.co.uk/basicorg/...tructural.html
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    Who does AS chemistry AQA because I want to revise with someone but I can't find any threads for people who do AQA chem
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    (Original post by hideNfreak)
    Who does AS chemistry AQA because I want to revise with someone but I can't find any threads for people who do AQA chem
    http://www.thestudentroom.co.uk/show...353273&page=28

    I'm doing AQA, there is a thread here
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    (Original post by hibaj)
    hey.

    if they ask for an equation and you write it as a displayed formula but mark scheme has it as molecular formula do you still get the marks?

    this is for ocr f322
    Unless they specify which form they want it in, then you should get the marks. In mark schemes, there's usually a sentence saying on the question saying which formulae are accepted, and it's usually skeletal, displayed and structural (more may be accepted but idk).
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    (Original post by lukejoshjames)
    Unless they specify which form they want it in, then you should get the marks. In mark schemes, there's usually a sentence saying on the question saying which formulae are accepted, and it's usually skeletal, displayed and structural (more may be accepted but idk).
    Ya, thanks. Was wondering what happens if they don't say that in the mark scheme and there's on one formula shown
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    Hi, do the intermolecular forces of halogenoalkanes decrease or increase down the group?

    Because I swear the boiling points of halogenoalkanes increases down the group due to larger & more halogen atoms. So shouldn't their intermolecular forces increase too?

    But a flashcard said that the C-X bonds get weaker as you go down due to shared electrons in a bond getting further from the halogen nucleus
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    (Original post by Nick-F007)
    For June 2010, 1 a) iii)

    How is the bond enthalpy for the products more than the reactants????
    Bond forming is exothermic
    Bond breaking is endothermic
    Bond enthalpy is the enthalpy change when breaking a mole of gaseous bonds to form gaseous atoms. So it is endothermic.
    However this reaction is exothermic because bonds are forming and bond enthalpy's sign is changed from + to - with same magnitude.
    So the bond enthalpy of products are bigger but when calculating the enthalpy change of the reaction using bond enthalpy you'd change the sign on the bond enthalpy of products to - so when added together with bond enthalpy of reactants the result ends up being negative = exothermic
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    (Original post by KINGYusuf)
    Hi, do the intermolecular forces of halogenoalkanes decrease or increase down the group?

    Because I swear the boiling points of halogenoalkanes increases down the group due to larger & more halogen atoms. So shouldn't their intermolecular forces increase too?

    But a flashcard said that the C-X bonds get weaker as you go down due to shared electrons in a bond getting further from the halogen nucleus
    Intermolecular forces of halogenoalkanes increase down the group because there are more electrons so stronger dispersion force.

    About C-X bonds getting weaker, it has got nothing to do with the boiling point. You probably had it written down for the rate of hydrolysis of halogenoalkanes.
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    Can someone describe/ show me the different boltzmann distribution graph for temperature, pressure and catalyst? Thanks
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    (Original post by xMillnsy)
    Can someone describe/ show me the different boltzmann distribution graph for temperature, pressure and catalyst? Thanks
    http://www.chemguide.co.uk/physical/...mperature.html
    http://www.chemguide.co.uk/physical/.../catalyst.html
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    Thank you
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    (Original post by KINGYusuf)
    Hi, do the intermolecular forces of halogenoalkanes decrease or increase down the group?

    Because I swear the boiling points of halogenoalkanes increases down the group due to larger & more halogen atoms. So shouldn't their intermolecular forces increase too?

    But a flashcard said that the C-X bonds get weaker as you go down due to shared electrons in a bond getting further from the halogen nucleus
    Both points are correct.

    Halogens exist as diatomic molecules and have van der Waal's forces between molecules and their neighbouring molecules. When you go down the group, the number of electrons increase and so the number of temporary dipoles and induced dipoles increase. Hence, boiling point and melting points increase as well.

    When halogens are bonded to another element (C-X), they are bonded covalently. So yeah, when the distance between the bonding electrons and nuclei increases, the bond strength decreases.

    I can't really form a straightforward answer as to why it seems contradictory, but I think it's because it's two different types of forces. van der Waal's is intermolecular and halogens change state when they are broken (i.e melt and boil). Covalent bonds are intramolecular and much stronger and between atoms, not molecules.

    And I guess you'd already know this but I figured it was worth mentioning just in case. For halogens in their diatomic state, bond enthalpy decreases from Chlorine. Fluorine has a lower bond enthalpy than Chlorine due to its short bond length causing lone pairs to repel each other.
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    Heterogeneous catalysts explained please? :blushing:
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    [CuCl2]-

    charge cl2= -1 and Cu= +1 ??

    How?

    is it because Cl is -1 then x2 = -2 and +1 because there is a negative charge?
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    (Original post by TheonlyMrsHolmes)
    [CuCl2]-

    charge cl2= -1 and Cu= +1 ??

    How?

    is it because Cl is -1 then x2 = -2 and +1 because there is a negative charge?

    Overall charge = -1

    Cu: X

    Cl2 = -1

    (X) + (2*-1) = -1
    (X) + (-2) = -1
    X = -1 + 2
    X = +1
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    (Original post by thymolphthalein)
    Overall charge = -1

    Cu: X

    Cl2 = -1

    (X) + (2*-1) = -1
    (X) + (-2) = -1
    X = -1 + 2
    X = +1
    I don't understand the -1 answer for 2 *-1? why is that. Sorry I'm so tired my brain has stopped making connections and reached a new stupidity level...
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    (Original post by Dinaa)
    Heterogeneous catalysts explained please? :blushing:
    Not on the spec. We only need to know specifics about catalytic converters
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    (Original post by Dinaa)
    Heterogeneous catalysts explained please? :blushing:
    A heterogeneous catalyst is one that is in a different phase (physical state) from the reactants.

    Eg: Iron powder catalyst (solid) in Haber process (Nitrogen and Hydrogen gas)

    I think only that much is required for AS.

    You have to remember three major steps later although I don't recall if it is required to know this in detail for AS.

    Heterogeneous. Adsorption. Reaction. Desorption. (H.A.R.D)

    Be careful NOT to write absorption.

    So for heterogeneous catalysts:

    Adsorption: Reactants are adsorbed onto the surface of the catalyst at the active sites, forming some weak bonds.

    Reaction: Rate of reaction is increased as adsorption weakens bonds within reactants (weakening activation energy) and changes the orientation of the molecules in such a way that greater proportion of successful collisions occur.

    Desorption: Products that are formed are desorbed from the surface and diffuse away from the catalyst
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    (Original post by TheonlyMrsHolmes)
    I don't understand the -1 answer for 2 *-1? why is that. Sorry I'm so tired my brain has stopped making connections and reached a new stupidity level...
    Aha, it's alright.

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    (Original post by itsConnor_)
    Not on the spec. We only need to know specifics about catalytic converters
    Which exams do you take?

    The Edexcel January 2015 IAL paper definitely had a question about heterogeneous catalysts and how they worked for two marks.
 
 
 
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