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    I need help with this question, any help is much appreciated.


    An organic liquid A contains only carbon, hydrogen and oxygen. The following observations are made on it.

    1. When A is mixed with bromine water, no change is observed.
    2. A has a molecular weight of 60, and contains 40% carbon and 6.7% hydrogen.
    3. A has no reaction with acidified potassium permanganate solution.
    4. When A is treated with lithium aluminium hydride, a compound B is produced. ( When propan-2-one is treated with lithium aluminium hydride a secondary alkanol is produced)
    5. B contains only carbon, hydrogen and oxygen, and has a molecular weight of 46. B contains 52.2% carbon and 13.1% hydrogen.

    Answer these questions.

    1. What is the molecular formula of A?
    2. What type of reagent is lithium aluminium hydride?
    3. What is the molecular formula of B?
    4. What is A?
    5. What is B?
    6. A and B react together to give a compound C and water. What is C and how would you set about obtaining a pure specimen of it?
    7. State the effects of A and B on universal indicator paper and explain the difference in these effects in term of the structure of the molecules.
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    (Original post by davidmarsh01)
    I need help with this question, any help is much appreciated.


    An organic liquid A contains only carbon, hydrogen and oxygen. The following observations are made on it.

    1. When A is mixed with bromine water, no change is observed.
    2. A has a molecular weight of 60, and contains 40% carbon and 6.7% hydrogen.

    Find out empirical formula of A from data given, first how much percent is oxygen in A?

    3. A has no reaction with acidified potassium permanganate solution.
    What does this mean, KMnO4 is a strong oxidising agent. What organic functional groups are not oxidised?

    4. When A is treated with lithium aluminium hydride, a compound B is produced. ( When propan-2-one is treated with lithium aluminium hydride a secondary alkanol is produced)
    LIAlH4 is a source of hydride, yes H-, this is a typical reaction for ketones, aldehydes, and maybe sometimes carboxylic acid, in short carbonyls.

    5. B contains only carbon, hydrogen and oxygen, and has a molecular weight of 46. B contains 52.2% carbon and 13.1% hydrogen.
    Again find empirical formula, then use molar mass to find molecular formula. Ask yourself what is the percentage of oxygen in B?

    Answer these questions.

    1. What is the molecular formula of A?
    2. What type of reagent is lithium aluminium hydride?
    3. What is the molecular formula of B?
    4. What is A?
    5. What is B?
    6. A and B react together to give a compound C and water. What is C and how would you set about obtaining a pure specimen of it?
    7. State the effects of A and B on universal indicator paper and explain the difference in these effects in term of the structure of the molecules.
    Hope the hints help.
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    1) Bromine water will react with double bonds and turns colourless. So you have no double bond.
    2) What percentage of the molecular weight is carbon (divide by 100, x 40), and so how many carbon atoms are there? Same with hydrogen. How many atomic mass units are left and what atoms could this be?
    3) Potassium permanganate is an oxidising agent. A cannot be oxidised.
    4) Lithium aluminium hydride is a reducing agent, so A is reduced to B.
    5) Do the same as 2 and compare the results. It may be easier to work out what B is and then mentally oxidise it to A.
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    Thanks for the hints, but i don't think you've really helped me answer the 7 questions down the bottom much, especially number 7
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    i meant 6 ^^
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    (Original post by davidmarsh01)
    i meant 6 ^^
    If you have two organic compounds reacting together at A' level they are invariably acid and alcohol giving ester...
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    (Original post by charco)
    If you have two organic compounds reacting together at A' level they are invariably acid and alcohol giving ester...
    How would you get a pure sample? And number 7 is also causing some difficulty if you would lke to help
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    (Original post by davidmarsh01)
    How would you get a pure sample? And number 7 is also causing some difficulty if you would lke to help
    What methods are there for purifying a non-miscible aqueous liquid (the ester)?

    7. What do you imagine will be the effect of an acid on indicator paper? and an alcohol?
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    (Original post by charco)
    What methods are there for purifying a non-miscible aqueous liquid (the ester)?

    7. What do you imagine will be the effect of an acid on indicator paper? and an alcohol?
    Oi! Stop being so derisory....it may be easy for some.....
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    (Original post by davidmarsh01)
    Oi! Stop being so derisory....it may be easy for some.....
    Touchy!

    My intention was to nudge you in the right direction...
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    (Original post by charco)
    Touchy!

    My intention was to nudge you in the right direction...
    Ok sorry then It's all good.
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    (Original post by charco)
    Touchy!

    My intention was to nudge you in the right direction...
    And how do you purify the ester?
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    (Original post by davidmarsh01)
    And how do you purify the ester?
    purify ie remove by-products; like charco mentioned before, ester is immiscible, by-product include the catalyst acid used(aqueous solution).

    think about how do you separate oil and water?
 
 
 
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