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Chemistry: Post your doubts here!

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

  1. Gémeaux

    Gémeaux

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    cud anyone post here sum link fr lectures on carbonyl componds???? plzzzzzz =(
     
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  3. sweetiepie

    sweetiepie

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  4. Gémeaux

    Gémeaux

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    thankuu
     
  5. sweetiepie

    sweetiepie

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    welcum anything esle post here or pm me :)
     
  6. NehaKush

    NehaKush

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    hi.. i need help in paper5.. i don't know how to do those question
     
  7. yubakkk

    yubakkk

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    can any one make me clear on sn1 and sn2??
     
  8. yubakkk

    yubakkk

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  9. hassam

    hassam

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  10. karishma92

    karishma92

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    1 You are provided with the following.
    FB 1, 3.00 mol dm–3 hydrochloric acid, HCl
    Three tubes containing different mixtures of sodium carbonate, Na2CO3, and sodium
    hydrogencarbonate, NaHCO3, each with a total mass of 5.00 g of mixture.
    tube labelled mass of Na2CO3 / g mass of NaHCO3 / g % by mass of Na2CO3
    FB 2 1.00 4.00 20.0
    FB 3 2.50 2.50 50.0
    FB 4 4.00 1.00 80.0
    You are to determine the temperature change, ΔT, when the contents of each of the tubes FB 2,
    FB 3 and FB 4 react with an excess of hydrochloric acid, FB 1.

    (a) (i) Calculate the volume of 3.00 mol dm–3 hydrochloric acid required to react with 5.00 g
    of sodium carbonate, Na2CO3. Show your working.
    Na2CO3(s) + 2HCl(aq) → 2NaCl(aq) + H2O(l) + CO2(g)
    [Mr: Na2CO3, 106.0]

    (ii) Calculate the volume of 3.00 mol dm–3 hydrochloric acid required to react with 5.00 g
    of sodium hydrogencarbonate, NaHCO3. Show your working.
    NaHCO3(s) + HCl(aq) → NaCl(aq) + H2O(l) + CO2(g)
    [Mr: NaHCO3, 84.0]

    pleaseeee HELP...
     
  11. waleed10

    waleed10

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    tell me something about chem 33 tomo
     
  12. yubakkk

    yubakkk

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    mole of hcl=2*mole of na2co3
    v of hcl= 2*(5\(106*3)
    =31.45 cm^3


    in ii
    maole of hcl = mole of nahco3
    v=7.5\(84*3)
    = 19.84
     
  13. abcd888

    abcd888

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    help in chemistry questions...

    1. Hydrogen bonding can occur between molecules of methanol, HCHO, and molecules of liquid Y. What could liquid Y be? A. CH3OH B. CH3CHO, C. CH3COCH3 D. CH3CO2CH3

    2. which solid exhibits more than one kind of chemical bonding? A. brass B. copper. C.diamond D. metallic

    3. which compound has boiling pint which is influenced by hydrogen bonding? A. CH3CHO B. CH3OCH3 C. HCO2H D. HCO2CH3

    4. Describe the bonding present in: Solid Krypton Kr and Solid Rubidium Rb

    5. HCN reacts with ethanol, CH3CHO. Give the displayed formula of the organic product formed. and what type of reaction is this?

    Please also explain
     
  14. XPFMember

    XPFMember XPC Moderator Staff Member

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    Assalamoalaikum!!

    You are probably, doing some mistake!
    E(CELL)=E(+ve)-E(-VE ELECTRODE)

    0.76 = 0.34 - E(-ve)

    E(-ve) = 0.34 - 0.76
    = -0.42 V
     
  15. kewaldoshi

    kewaldoshi

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    can someone please post all the formulas needed for stoichiometery
     
  16. sweetiepie

    sweetiepie

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  17. AkhlaqAhmed

    AkhlaqAhmed

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    there's a doubt in the chem paper 31 m/j 2011 q1 c (iii)....ER says that we're supposed to use our answer from c(ii) instead of using the approximate conc. given above.....how do we calculate using the answer in c(ii)???????.......plzzzzz REPLY FAST since i have my chem practical exam today at 12pm!!!!!!!!!!!
     
  18. vaishster

    vaishster

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    i wrote enthapy of neutr as 58.1.. (i think it ws 57).. will i get mark ??
     
  19. nikhilthomas

    nikhilthomas

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    the ans has to in 57 so u won't get mark
     
  20. AkhlaqAhmed

    AkhlaqAhmed

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    Firstly, if you had paper 33 then this is for you, and secondly, if you didn't get the right answer you will get marks for the formula that you used (which should be the multiplication between 4.3J, temperature change and the volume that you got at the point of intersection in the graph)
     
  21. rahulsharma

    rahulsharma

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    Re: All Chemistry help here!! Stuck somewhere? Ask here!

    u must see which is more positive E value. For this case the Chromate is more +ve...it shud be written the same way..that is no inverse. The Cl- equation should be reverse as it less +ve!

    Hope tht helps :)
     

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