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OCR Chemistry F322~ 4th June 2013~ AS Chemistry Watch

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    (Original post by GeneralOJB)
    Gotta love people asking for help on past paper questions when the exam is in 2 hours.
    Just starting doing the exam past papers.
    In fact, i'm not even going to do them, just going through them with the mark schemes.
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    Okay litterally panicking now..CAN ANYBODY CONFIRM THIS FOR ME. WHEN TOLD TO WORK OUT STANDARD ENTHALPY CHANGE OF COMBUSTION AND WE ARE GIVING THE CHANGE OF FORMATION. DO WE NEED TO SWITCH SIGNS AT THE END??
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    (Original post by SheriB)
    Okay litterally panicking now..CAN ANYBODY CONFIRM THIS FOR ME. WHEN TOLD TO WORK OUT STANDARD ENTHALPY CHANGE OF COMBUSTION AND WE ARE GIVING THE CHANGE OF FORMATION. DO WE NEED TO SWITCH SIGNS AT THE END??
    Just draw a Hess cycle...
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    (Original post by tryingtolearn95)
    Need help with questions on the specimen paper:
    Attaching the two questions. The issue I have with them is written in the pictures.
    Please help. Panicking rn
    Attachment 223034
    Attachment 223035


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    Alot of the answers are wrong on the specimen
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    (Original post by SheriB)
    Okay litterally panicking now..CAN ANYBODY CONFIRM THIS FOR ME. WHEN TOLD TO WORK OUT STANDARD ENTHALPY CHANGE OF COMBUSTION AND WE ARE GIVING THE CHANGE OF FORMATION. DO WE NEED TO SWITCH SIGNS AT THE END??
    Just look at the table given, if formation products - Reactants but if table gives combustion do Reactants - Products


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    (Original post by SheriB)
    Okay litterally panicking now..CAN ANYBODY CONFIRM THIS FOR ME. WHEN TOLD TO WORK OUT STANDARD ENTHALPY CHANGE OF COMBUSTION AND WE ARE GIVING THE CHANGE OF FORMATION. DO WE NEED TO SWITCH SIGNS AT THE END??
    If you draw out a Hess' cycle any time that you go against an arrow you need to switch the sign of the energy change. Hope this helps a bit
    Don't panic
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    Just to confirm is this correct:
    Oxidising a primary alcohol by distillation, an oxidising agent, heat and an acid catalyst produces a aldehyde.
    Oxidising a primary alcohol under reflux, heat and an oxidising agent produces a carboxylic acid.
    Oxidising a secondary alcohol under reflux, an acid catalyst, heat and an oxidising agent produces a ketone.

    A few questions, does producing a carboxylic acid require a catalyst (I don't think it does but want to make sure)? Also does making a ketone require only acidic conditions, not a actual catalyst or are they the same thing?
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    (Original post by CRW1996)
    Just to confirm is this correct:
    Oxidising a primary alcohol by distillation, an oxidising agent, heat and an acid catalyst produces a aldehyde.
    Oxidising a primary alcohol under reflux, heat and an oxidising agent produces a carboxylic acid.
    Oxidising a secondary alcohol under reflux, an acid catalyst, heat and an oxidising agent produces a ketone.

    A few questions, does producing a carboxylic acid require a catalyst (I don't think it does but want to make sure)? Also does making a ketone require only acidic conditions, not a actual catalyst or are they the same thing?
    That's right only you don't need a catalyst for any of these reactions. In all of the reactions the oxidising agent needs to be acidified not just for secondary alcohols
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    (Original post by CRW1996)
    Just to confirm is this correct:
    Oxidising a primary alcohol by distillation, an oxidising agent, heat and an acid catalyst produces a aldehyde.
    Oxidising a primary alcohol under reflux, heat and an oxidising agent produces a carboxylic acid.
    Oxidising a secondary alcohol under reflux, an acid catalyst, heat and an oxidising agent produces a ketone.

    A few questions, does producing a carboxylic acid require a catalyst (I don't think it does but want to make sure)? Also does making a ketone require only acidic conditions, not a actual catalyst or are they the same thing?
    Yes.
    Yes.
    Yes.

    Oxidising alcohols always requires an acid catalyst, normally h2so4.
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    (Original post by SheriB)
    Okay litterally panicking now..CAN ANYBODY CONFIRM THIS FOR ME. WHEN TOLD TO WORK OUT STANDARD ENTHALPY CHANGE OF COMBUSTION AND WE ARE GIVING THE CHANGE OF FORMATION. DO WE NEED TO SWITCH SIGNS AT THE END??
    Delta H equals given enthalpies of:
    formation, products - reactants
    Combustion, reactants - products
    Bond enthalpies, reactants - products
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    (Original post by CRW1996)
    Just to confirm is this correct:
    Oxidising a primary alcohol by distillation, an oxidising agent, heat and an acid catalyst produces a aldehyde.
    Oxidising a primary alcohol under reflux, heat and an oxidising agent produces a carboxylic acid.
    Oxidising a secondary alcohol under reflux, an acid catalyst, heat and an oxidising agent produces a ketone.

    A few questions, does producing a carboxylic acid require a catalyst (I don't think it does but want to make sure)? Also does making a ketone require only acidic conditions, not a actual catalyst or are they the same thing?
    I believe you have to know that the acid catalyst is acidified potassium dichromate. Which you use for both primary and secondary alcohols
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    (Original post by GeneralOJB)
    Yes.
    Yes.
    Yes.

    Oxidising alcohols always requires an acid catalyst, normally h2so4.
    Ok thank you
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    can someone please explain how jun 2012, Q4eii and jan 2012, 3bii. is done please. thanks in advance
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    Is enthalpy change of reaction the same as enthalpy change of formation as in they're always products - reactants?

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    (Original post by Liberty.)
    I believe you have to know that the acid catalyst is acidified potassium dichromate. Which you use for both primary and secondary alcohols
    noo. catalyst is sulphuric acid. Potassium dichromate is used in the reaction.
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    Good Luck everyone! Hope u guys do well
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    that's confusing. I usually use the sum of enthalpy of reactants - products
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    For nucleophillic substitution,
    When there are two cl atoms, can we replace both with OH?

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    (Original post by GeneralOJB)
    Gotta love people asking for help on past paper questions when the exam is in 2 hours.
    Please help with my question above
    Ty


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    (Original post by SAS18)
    first post
    thanks good luck everyone
 
 
 
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