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    1. A mixture of the oxides of two elements of the third period is dissolved in water. The solution is approximately neutral.
    What could be the constituents of the mixture?

    This is a multiple choice question and the answer is Na2O and P4O10
    does P4O10 become acid when reacting water? why?





    2. Aluminium chloride catalyses certain reactions by forming carbocations with chloroalkanes as shown.

    RCl + AlCl3 -> R+ + AlCl-4
    Which property makes this reaction possible?

    the answer is " The aluminium atom in AlCl3 has an incomplete octet of electrons.

    why AlCl3 is octet?






    3. The compound hex-3-en-1-ol, P, has a strong 'leafy' smell of newly cut grass and is used in perfumery.

    P = CH3CH2CH = CHCH2CH2OH

    What is produced when P is treated with an excess of hot concentrated acidic KMnO4?

    the answer is CH3CH2CO2H and
    HO2CCH2CO2H

    I can see that calboxylic acid should be formed with alcohol, but I don't know why calboxylic acid is formed from C which doesn't have alcohol





    4. The product of the reaction between propanone and hydrogen cyanide is hydrolysed under acidic conditions.

    What is the formula of the final product?

    the answer is (CH3)2C(OH)CO2H

    don't know why




    thank you! :tsr:
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    Off the top of my head i can only answer the 4th question.

    Propanone is CH3C=OCH3

    If you add HCN to this you get CH3COH(CN)CH3

    Addding the acid (with water) converts the CN to a COOH group.

    CH3COH(COOH)CH3

    There are explanation to these but you don't really need to know them for A-level chem (though you may need to know the mechanism for the first one). You simply have to sit down and learn the reactions, reagents and conditions.
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    (Original post by ba_ba1)
    Off the top of my head i can only answer the 4th question.

    Propanone is CH3C=OCH3

    If you add HCN to this you get CH3COH(CN)CH3

    Addding the acid (with water) converts the CN to a COOH group.

    CH3COH(COOH)CH3

    There are explanation to these but you don't really need to know them for A-level chem (though you may need to know the mechanism for the first one). You simply have to sit down and learn the reactions, reagents and conditions.
    thanks , I'm doing AS right now
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    (Original post by rlagksquf)
    1. A mixture of the oxides of two elements of the third period is dissolved in water. The solution is approximately neutral.
    What could be the constituents of the mixture?

    This is a multiple choice question and the answer is Na2O and P4O10
    does P4O10 become acid when reacting water? why?
    Phosphorus is a non metal and forms an acidic oxide.

    2P4O10 + 6H2O --> 4H3PO4



    (Original post by rlagksquf)
    2. Aluminium chloride catalyses certain reactions by forming carbocations with chloroalkanes as shown.

    RCl + AlCl3 -> R+ + AlCl-4
    Which property makes this reaction possible?

    the answer is " The aluminium atom in AlCl3 has an incomplete octet of electrons.

    why AlCl3 is octet?
    AlCl3 is electron deficient in that the Al only has 6 electrons in its outer shell. It can easily accept and electron pair from other species - this is the basis of its lewis acid behaviour.






    (Original post by rlagksquf)
    3. The compound hex-3-en-1-ol, P, has a strong 'leafy' smell of newly cut grass and is used in perfumery.

    P = CH3CH2CH = CHCH2CH2OH

    What is produced when P is treated with an excess of hot concentrated acidic KMnO4?

    the answer is CH3CH2CO2H and
    HO2CCH2CO2H

    I can see that calboxylic acid should be formed with alcohol, but I don't know why calboxylic acid is formed from C which doesn't have alcohol?

    the manganate VII ion can oxidise the double bond via a diol addition product.

    eg CH2=CH2 ---> CH2(OH)-CH2(OH)

    this is then urther oxidised cleaving the carbon-carbon bond and making a carboxylic acid at the end.
 
 
 
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