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Chemistry: Post your doubts here!

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

  1. Jane_Kim

    Jane_Kim

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    How do u solve this question? Can anyone help me? The question is from 2018 Oct/Nov paper 12. The answer is A.
     

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  3. Jane_Kim

    Jane_Kim

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    I think I can explain this! So if you see the periodic table, potassium is below the sodium.
    - Potassium is in period 4 and Sodium is in period 3 but they belong to the same group.
    - Potassium's atomic number is 19 while the Sodium's is 11. Potassium > Sodium (in terms of number of electrons).
    - Using Aufbau principle
    K= 1s2, 2s2, 2p6, 3s2, 3p6, 4s1
    Na= 1s2, 2s2, 2p6, 3s1

    - Electron configuration
    K= 2,8,8,1
    Na= 2,8,1

    Hence, we can say that potassium occupies one more shell than sodium.

    K+ and Na+. Both mean that they lose one electron from their outermost electron shell.
    Losing one electron will make potassium to become full 3rd shell and sodium to become full 2nd shell.
    So basically it's like,
    K+= 1s2, 2s2, 2p6, 3s2, 3p6
    Na+= 1s2, 2s2, 2p6

    Therefore K+ has a greater ionic radius than Na+

    Hope you get my point my friend!
     

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  4. Hamnah Zahoor

    Hamnah Zahoor

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    Reaction with 2,4-dinitrophenylhydrazine shows the presence of either an aldehyde or a ketone.
    Check the options a positive result will be shown with option A,B,D
    Decolourising of pottasium magnate shows oxidation took place option A and D
    And the emperical formula shown of C2H3O is only consistent with option A i.e C4H6O2-------->C2H3O
    Thus,correct option is A.
     
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  5. Jane_Kim

    Jane_Kim

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    "Decolourising of pottasium magnate shows oxidation took place option A and D"... I don't get why...? Can you explain more on that?? Thank youuu!!
     
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  6. Hamnah Zahoor

    Hamnah Zahoor

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    Potassium magnate is an oxidizing agent it is originally purple in colour and on oxidizing it becomes colourless.
    In option A the aldehyde will be oxidized to carboxylic acid thus Oxidation took place.
    In option D on the right side of the compound there is also an aldehyde which oxidizes.
     
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  7. Jane_Kim

    Jane_Kim

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    Hiiii this is from 2018 Feb March paper 12. The answer is A. Can anyone explain why...? Thanksssss!
     

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  8. Hamnah Zahoor

    Hamnah Zahoor

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    Capture.PNG
     
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  9. Jane_Kim

    Jane_Kim

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    Ohhh yes got it thank youuu
     
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  10. Jane_Kim

    Jane_Kim

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    This question is from 2018 October November Paper 12. The answer is D. Can anyone help me with this? Thank you!
     

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  11. Hamnah Zahoor

    Hamnah Zahoor

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    565.PNG
    7897.PNG
     
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  12. Jane_Kim

    Jane_Kim

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    Thank you so much I get it now!!
     
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  13. Mistar-Kigi

    Mistar-Kigi

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    It's that time of the year again xD
     
  14. Hamnah Zahoor

    Hamnah Zahoor

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    You are welcome
     
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  15. Mistar-Kigi

    Mistar-Kigi

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    Quick question : When writing an ionic equation from the list in the data booklet , we choose the ones which give us the most Potential difference , right?
     
  16. Jane_Kim

    Jane_Kim

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    Hi I have another question here. This is from MayJune 2018 paper 11. The answer is C... How do u solve this??
     

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  17. Jane_Kim

    Jane_Kim

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    I'm not quite sure about it. Sorry...
     
  18. Mistar-Kigi

    Mistar-Kigi

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    Hot concentrated KmnO4 causes rupture at the double bond. Thus, you break both the double bonds and form ketone and carboxylic acid (according to the arrangement). Also, do remember that CO2 is always produced during rupture.

    I'm not the best when it comes to explaining so if it doesn't clear that up just reply and I'll try sending you a picture.



    Edit : Methanioc acid would be a product too but since it's not mentioned we ignore it.
     
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  19. Jane_Kim

    Jane_Kim

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    Sorry I still don't really get it... Can I see the picture?? Thank you so much!
     
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  20. Mistar-Kigi

    Mistar-Kigi

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    Here you are
    I tried but it says that the file size is too big sorry ;-;
     
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  21. Mistar-Kigi

    Mistar-Kigi

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    Also, is there literally anyone who can clear this up?
     

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