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Chemistry: Post your doubts here!

Discussion in 'International A And AS Level' started by XPFMember, Sep 29, 2011.

  1. Unknown202

    Unknown202

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    [​IMG]
     
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  3. Unknown202

    Unknown202

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    i need a help in this question why is it A?
     
  4. studyingrobot457

    studyingrobot457

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    no image
     
  5. Unknown202

    Unknown202

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  6. Unknown202

    Unknown202

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    Now ?!
     
  7. Hamnah Zahoor

    Hamnah Zahoor

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    When ever two stages are involved in reaction its ethalpy profile diagram will have two humps in its graph .......as it is stated in the question X-Y is positive thus it will be endo and reactants will have low energy than the products....in Y-Z ethalpy change is neg thus its exo and reactants will have high energy than products as shown in option A
     
  8. Unknown202

    Unknown202

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    So it can't be B r8
     
  9. Hamnah Zahoor

    Hamnah Zahoor

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    No....no humps in the graph
     
  10. Unknown202

    Unknown202

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    K thx soo much:LOL::)
     
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  11. MShaheerUddin

    MShaheerUddin

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  12. sweetiepie94

    sweetiepie94

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  13. MnMz Mohammad-M

    MnMz Mohammad-M

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    The balanced equation should be 10Al + 3Ba(NO3)2 = 5Al2O3 + 3BaO + 3N2 , right? therefore we will get a different answer..
    plz reply as soon as possible..
     
  14. Tigercub

    Tigercub

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    Can anyone help me please?
    What is involved in the mechanism of the mechanism of the reaction between aqueous sodium hydroxide and 2-bromo-2-methylbutane?
    A heterolytic bond fission, attack by an electrophile on a carbanion
    B heterolytic bond fission, attack by an nucleophile on a carbocation
    C homolytic bond fission, attack by an electrophile on a carbanion
    D homolytic bond fission, attack by an nucleophile on a carbocation
     
  15. Metanoia

    Metanoia

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    2-bromo-2-methylbutane is a tertiary halogenoalkane and will undergo sN1 'unimolecular' via carbocation reactions.

    [​IMG]

    The C-Br bond will be broken heterolytically and a carbocation ion will be formed. The carbocation would then be attacked by the nucleophile (OH-)
     
  16. Metanoia

    Metanoia

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    I don't have the context of the full question.

    But in both equations, the ratio of Ba(NO3)2 and N2 happens to be 1:1. Therefore, it's a coincidence that the answers ended up to be the same.
     
  17. MShaheerUddin

    MShaheerUddin

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    Can you answer my question please?
     
  18. fahadhameedahmad

    fahadhameedahmad

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    are you talking about this question
     
  19. MShaheerUddin

    MShaheerUddin

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    [​IMG]
     
  20. Daveen

    Daveen

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    Hey download this app called A level chemistry by overdose
    available on playstore
     

    Attached Files:

  21. fahadhameedahmad

    fahadhameedahmad

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    lime stone is CaCO3
    lime is CaO or Ca(OH)2
    now all three would react with acids because acids react with carbonates (CaCO3) and bases (CaO/Ca(OH)2)

    But old lime mortar effervesces (which means produces a gas), so this would be CaCO3 as it would produce CO2 gas with HCl

    between A and D, D would be correct as water is present as well so quiklime would be Ca(OH)2
     
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