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Chemistry: Post your doubts here!

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

  1. Hamnah Zahoor

    Hamnah Zahoor

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    Capture.PNG
     
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  3. Hamnah Zahoor

    Hamnah Zahoor

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    Whenever it says file size too big just take a screenshot of the picture you want then post it.
     
  4. Mistar-Kigi

    Mistar-Kigi

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    Got it! thank you.

    Can you please help me with my question though?
     
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  5. Hamnah Zahoor

    Hamnah Zahoor

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    Sorry I don't know the answer.
     
  6. Jane_Kim

    Jane_Kim

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    Hi, can anyone help me solving this question? This is taken from 2017 MJ 12. The answer should be D.
     

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  7. Sabahyder

    Sabahyder

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    Pls help me with paper 34 May June 2016 chemistry. How to find the dilution factor?
    Qs 1 c part
     
  8. desterman

    desterman

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    Where can I get notes that follow the syllabus and explains each learning outcome without adding extra unnecessary information. If there is for chemistry, is there also for biology and physics?
     
  9. Mistar-Kigi

    Mistar-Kigi

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    Try Znotes, they'd probably have it all. As for chemistry chemguide is pretty good!
     
  10. Mistar-Kigi

    Mistar-Kigi

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    Heating an alcohol with H2SO4 would dehydrate it and result in alkene formation. If you heat A,B or C , you have 2 options for a double bond in all of them ( double will come between the OH carbon and the carbon next to it, That can be on either side whicj would result in mixture of both compounds ). However, in D there is only one carbon beside OH carbon so there's just one possibility.
     
  11. desterman

    desterman

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    Do you have others? Also can you get chemguide as a pdf file?
     
  12. Panchod Ijaz

    Panchod Ijaz

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    which ions are present in a solution of ethanol in an excess of concentrated sulphuric acid?
    1) CH3CH2O^-1
    2) CH3CH2^+OH2
    3) HSO4^-1
     
  13. Mistar-Kigi

    Mistar-Kigi

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    Not sure ummm but 2&3?
     
  14. Metanoia

    Metanoia

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    1) is definitely out as it requires the OH group to act as an acid and release a H+ . which is not possible in the presence of H2SO4
     
  15. Emmris

    Emmris

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  16. MShaheerUddin

    MShaheerUddin

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    Screenshot_20190322-030856.png
    Can anyone tell me why in a(ii) they multipled experiment 1's initial rate with 27 to get K?
    where that 27 came from?
    explain?
     
  17. MShaheerUddin

    MShaheerUddin

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    The two equations are:

    CH4 + 2O2 --> CO2 + 2H2O
    CH4 + 3/2O2 --> CO + 2H2O

    multiply equation 1 by 99 and add to equation 2

    99CH4 + 198O2 --> 99CO2 + 198H2O
    CH4 + 3/2O2 --> CO + 2H2O
    ---------------------------------------------------------------------------------------- add
    100CH4 + 199(1/2)O2 --> 99CO2 + CO + 200H2O

    So, burning 100 moles needs 199(1/2) moles of oxygen


    Therefore burning y moles needs 2y - y/200

    or expressed as a decimal fraction:

    2y - (0.01/2)y

    i.e. answer A
     
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  18. Mistar-Kigi

    Mistar-Kigi

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    Reaction is first order wrt O2 and 2nd order wrt NO. So concentration of NO is increased 3 times as well as [O2]. You get (3^2) x 3 considering the orders which'd give you 27 times the rate in reaction 1.


    Edit : An alternative way would be to calculate the rate constant using any experiment of your choice and then using it along with concentrations in the 4th experiment to get your desired rate.
     
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  19. MShaheerUddin

    MShaheerUddin

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    bro where did this 3 came from?
     
  20. Mistar-Kigi

    Mistar-Kigi

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    O2 is first order and it's concentration is tripled [3]^1 will be 3
     
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  21. MShaheerUddin

    MShaheerUddin

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    upload_2019-3-22_15-39-22.png
    Please help me with this one too.. ?
    What is the procedure of building these sort of equations and then telling which is the slow one?
     

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