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  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    13,415 posts since May '05
    • Originally posted by hoay:

      Sure this is the link for Question paper, MS.

      http://pastpapers.papacambridge.com/view.php?id=Cambridge%20International%20Examinations%20%28CIE%29/AS%20and%20A%20Level/Chemistry%20%289701%29/2016%20Nov/9701_w16_qp_12.pdf

       

      http://pastpapers.papacambridge.com/view.php?id=Cambridge%20International%20Examinations%20%28CIE%29/AS%20and%20A%20Level/Chemistry%20%289701%29/2016%20Nov/9701_w16_ms_12.pdf

       

      The examiners' report for this question states:

      29% of candidates chose the correct answer C. The mst commonly chosen answer was D chosen by 29% of candidates. If a fixed mass of gas is behaving ideally the sum PV/RT gives a constant value. for both the conditions given in the question

      PV/RT =6.418 (if volume of 1dm3 and 0.5 dm3 are assumed. therefore gas is behaving ideally.

      the paper is NOV 2016/12/Q.8

       

       


      Cambridge and I are both correct. The error is yours, hoay. You gave the wrong temperature after compression.

      Using Cambridge values, nR (before compression) / nR (after compression) = 1.00, hence the gas is behaving ideally.

      In future to avoid typos, you can directly post the online link to the question and mark scheme, instead of typing out the question.

  • hoay's Avatar
    166 posts since Jul '11
  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    13,415 posts since May '05
    • Originally posted by hoay:

      Yes my mistake....My apologies. I did not check the temperature.

       

       


      No prob. Hope it helped to clear up your doubts.

  • hoay's Avatar
    166 posts since Jul '11
    • Yes i come to know the compression factor. 

      Sometimes the gas Dimerizes this reduces the no of gas molecules...When the gas dimerizes ? is it related to temperature? I know of ethanoic dimerizing but that is due to Extensive H-bonding...is this anything to do with Ideal beahviour?

  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    13,415 posts since May '05
    • Originally posted by hoay:

      Yes i come to know the compression factor. 

      Sometimes the gas Dimerizes this reduces the no of gas molecules...When the gas dimerizes ? is it related to temperature? I know of ethanoic dimerizing but that is due to Extensive H-bonding...is this anything to do with Ideal beahviour?


      Gases which dimerize and monomerize are a select few, for A level purposes, most notably NO2 monomer which exists in equilibrium with N2O4 dimer, via a free radical mechanism. (Of courser, there's AlCl3 and Al2Cl6, but that's (s), (l), (g), (g) equilibria, and involves polymeric lattice structure in solid state as well, dimerization mechanism via dative covalent bonding).

      Yes, it's related to temperature, enthalpy and entropy, all 3 variables incorporated in Gibbs free energy. The NO2 - N2O4 equilibria is a perfect illustration of how all 4 variables are inter-connected, as well as how these 4 variables are connected to the shifting of position of equilibrium.

      image

      http://www.rsc.org/learn-chemistry/resource/res00001739/le-chateliers-principle-the-equilibrium-between-nitrogen-dioxide-and-dinitrogen-tetroxide

      Edited by UltimaOnline 08 Jun `17, 4:10PM
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