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Edexcel - Chemistry Unit 2 - 4 June 2013 Watch

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    I got the answer for this (A), but the question overall confused me. [from June 2011]
    Shouldn't a secondary alcohol be heated under reflux to give a ketone? Or is this just a case of choosing the "more correct answer"?
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    (Original post by SKK94)
    I got the answer for this (A), but the question overall confused me. [from June 2011]
    Shouldn't a secondary alcohol be heated under reflux to give a ketone? Or is this just a case of choosing the "more correct answer"?
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    what is the question about :confused:
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    (Original post by SKK94)
    I got the answer for this (A), but the question overall confused me. [from June 2011]
    Shouldn't a secondary alcohol be heated under reflux to give a ketone? Or is this just a case of choosing the "more correct answer"?
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    Nope you can use both... it's just that heat under reflux is typically used. The distillation part is not needed as it's not further oxidized but you can still use the apparatus


    (Original post by JRN-95)
    what is the question about :confused:
    Oxidation of Primary & Secondary alcohols... if you have not come across that yet, then I suggest you get reading my friend !
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    (Original post by Mollymod)
    ""

    Oooh I have high hopes now I wrote "To remove any acid from the food" then while the teachers were collecting the papers... I decided to open my paper up & just write "salt" as well for that question So hopefully I get 1 mark at least

    & I've firmed Computer Science at King's College London

    & yourself? Pharmacy ? ... something chemistry related definitely, judging from your TSR name
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    When answering questions about the halgenoalkane reactions such as the substitution and elimination ones, and the question says something like "How do you turn a halgenoalkane into a alcohol?" Would you answer by saying reflux with an aqueous alkali hydroxide or just alkali?

    Basically do you write alkali hydroxide or alkali?
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    (Original post by Jayqwe)
    When answering questions about the halgenoalkane reactions such as the substitution and elimination ones, and the question says something like "How do you turn a halgenoalkane into a alcohol?" Would you answer by saying reflux with an aqueous alkali hydroxide or just alkali?

    Basically do you write alkali hydroxide or alkali?
    Well I'd be more specific and say KOH or NaOH just to be safe, so in respect that's an alkaline hydroxide but they often want specifics.

    (Original post by posthumus)
    Oooh I have high hopes now I wrote "To remove any acid from the food" then while the teachers were collecting the papers... I decided to open my paper up & just write "salt" as well for that question So hopefully I get 1 mark at least

    & I've firmed Computer Science at King's College London

    & yourself? Pharmacy ? ... something chemistry related definitely, judging from your TSR name
    Yeah I'm pretty sure that as long as you have a plausible reason and back it up properly using Chemistry you should be fine.
    Biochemistry with a year abroad at Essex
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    (Original post by Mollymod)
    Well I'd be more specific and say KOH or NaOH just to be safe, so in respect that's an alkaline hydroxide but they often want specifics.
    Thank you
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    10. 20 cm3 of sulfuric acid, concentration 0.25 mol dm–3, was neutralized in a titration with barium hydroxide, concentration 0.50 mol dm–3. The equation for the reaction is
    Ba(OH)2(aq) + H2SO4(aq) → BaSO4(s) + 2H2O(l)

    (a) The volume of barium hydroxide required was (1)
    A 10 cm3
    B 20 cm3
    C 25 cm3
    D 40 cm3

    help anyone?
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    (Original post by pineapple78)
    10. 20 cm3 of sulfuric acid, concentration 0.25 mol dm–3, was neutralized in a titration with barium hydroxide, concentration 0.50 mol dm–3. The equation for the reaction is
    Ba(OH)2(aq) + H2SO4(aq) → BaSO4(s) + 2H2O(l)

    (a) The volume of barium hydroxide required was (1)
    A 10 cm3
    B 20 cm3
    C 25 cm3
    D 40 cm3

    help anyone?
    Is the answer A ? If so...

    The ratio between reaction of sulfuric acid & barium hydroxide is 1:1 ... therefore they must both equal the same amount of moles.

    moles = volume x concentration

    therefore... mole of sulfuric acid = 0.02 x 0.25 = 0.005

    there must also be 0.005 moles of barium hydroxide, therefore:

    volume= moles/ concentration = 0.005/ 0.5 = 0.01

    Woops my bad they want it in cm^3... here we have our answer in dm^3

    1dm^3 = 1000 cm^3
    so...

    0.01 x 1000 = 10 cm^3
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    January 2012, question 20(a)(iv).How do we find the concentration?The question is really big, so i'm not posting it!
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    (Original post by saifulahmed)
    January 2012, question 20(a)(iv).How do we find the concentration?The question is really big, so i'm not posting it!
    This is what I've come up with, let me know if it makes sense or not
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    (Original post by posthumus)
    Nope you can use both... it's just that heat under reflux is typically used. The distillation part is not needed as it's not further oxidized but you can still use the apparatus
    Oh! Thanks
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    I am terrified about this exam. I'm so scared it's going to be weird and difficult, not forgetting that the grade boundaries seem to be slowly climbing up
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    Hey, does anyone have any advice as to how to answer a section C question successfully - there's always that 6 mark question, and I always get it wrong.
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    Section c always has a random topic each time so that is hard say, also do we need to know how to turn an amine, alcohol and an alkene back to a halgenoalkane, or do we just need to know the forward reactions?

    Posted from TSR Mobile
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    (Original post by posthumus)
    Nope you can use both... it's just that heat under reflux is typically used. The distillation part is not needed as it's not further oxidized but you can still use the apparatus




    Oxidation of Primary & Secondary alcohols... if you have not come across that yet, then I suggest you get reading my friend !
    i understand primary, secondary and tertiary alcohols and their structure what i dont understand is when they say oxidised how can you work out what product is formed without doing the oxidation numbers?
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    Hii
    does anyone know apart from reflux and distilation, what other diagrams do we need to know?

    and does anyone know what diagram to draw for this question:


    Jan 2011 - Q13

    Draw a diagram of a seperating funnel containing the seperated layers! label the hydrocarbon and state its colour
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    (Original post by JRN-95)
    i understand primary, secondary and tertiary alcohols and their structure what i dont understand is when they say oxidised how can you work out what product is formed without doing the oxidation numbers?
    You don't do any oxidation numbers. When a primary alcohol is oxidised it always forms an aldehyde/carboxylic acid, when a secondary alcohol is oxidised it always forms a ketone and tertiary alcohols cannot be oxidised. For the product formed, draw out the structure of the alcohol and if it is a primary alcohol being oxidised into an aldehyde, you remove the -OH part and add a double bond =O and a -H to the carbon that was carrying the -OH. Similarly for secondary alcohols ketones, you remove the -OH and add a double bond =O to the carbon carrying the -OH.
    Read this: http://www.chemguide.co.uk/organicpr...oxidation.html
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    (Original post by Priya08)
    Hii
    does anyone know apart from reflux and distilation, what other diagrams do we need to know?

    and does anyone know what diagram to draw for this question:


    Jan 2011 - Q13

    Draw a diagram of a seperating funnel containing the seperated layers! label the hydrocarbon and state its colour


    It is basically that with a hydrocarbon layer and an aqueous layer
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    (Original post by scientific222)


    It is basically that with a hydrocarbon layer and an aqueous layer
    Omg thank you so muchh! and baiscally that oil layer is the hydrocarbon right? thanks again
 
 
 
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