H2 Chem Stoichiometry, Gaseous State

• CaiHongRainx

  12 Jun 13, 12:23

  Sorry for double posting.
• CaiHongRainx

  12 Jun 13, 12:27

  Hii, I have a few qns here. Miscellanous qn: Do we still need to know what's a mass spectrometer, NMR spectrum for H2 Chem? Stoichiometry: A giant molecule contains a large amount of carbon, mainly of isotopes 12C and 13C. It was found that the relative atomic mass of carbon in the molecule is 12.20. What is the ratio of 12C to 13C ? Ans: 4:1 It happens that this is a MCQ qn. So the approach is just (12x0.8) + (13x0.2) = 12.2 I was wondering, what if this is not a MCQ qn? I know we can let them be x and y. So it becomes 12x + 13y = 12.2 . However there is only one eqn. Gasesous State: Under extereme conditions, gallium chloride Ga2Cl6 can also be formed via the endothermic dimerisation of GaCl3. The two species can exist in dynamic equilibrium under suitable conditions. 2GaCl3(g) two way arrow Ga2Cl6(g) (1) In an experiment, a total pressure of 7.75 x 10^-3 N m^-2 was measured when a 0.661g sample of GaCl3 was allowed to dimerise in a 1.80dm3 vessel at 200 degrees. Calculate x, the fraction of GaCl3 that dimerised at 200 degrees, assuming ideal gas behaviour. I apply pV=nRT, where turns n is 0.00354904 Initial mass is 0.661g of GaCl3, n = 0.00375141 Fraction that dimerised, x = (0.00375141 - 0.00354904) / 0.00375141 = 0.053945 But the answer is 0.108! (No working provided) Thanks for answering!!!
• UltimaOnline

  12 Jun 13, 12:38

  Originally posted by CaiHongRainx:

  Hii, I have a few qns here.

  Miscellanous qn: Do we still need to know what’s a mass spectrometer, NMR spectrum for H2 Chem?

  Stoichiometry: A giant molecule contains a large amount of carbon, mainly of isotopes 12C and 13C. It was found that the relative atomic mass of carbon in the molecule is 12.20. What is the ratio of 12C to 13C ?
  Ans: 4:1

  It happens that this is a MCQ qn. So the approach is just (12×0. + (13×0.2) = 12.2
  I was wondering, what if this is not a MCQ qn? I know we can let them be x and y.
  So it becomes 12x + 13y = 12.2 . However there is only one eqn.

  Gasesous State: Under extereme conditions, gallium chloride Ga2Cl6 can also be formed via the endothermic dimerisation of GaCl3. The two species can exist in dynamic equilibrium under suitable conditions.
  2GaCl3(g) two way arrow Ga2Cl6(g)

  (1) In an experiment, a total pressure of 7.75×10^{-3 N m}-2 was measured when a 0.661g sample of GaCl3 was allowed to dimerise in a 1.80dm3 vessel at 200 degrees.

  Calculate x, the fraction of GaCl3 that dimerised at 200 degrees, assuming ideal gas behaviour.

  I apply pV=nRT, where turns n is 0.00354904

  Initial mass is 0.661g of GaCl3, n = 0.00375141

  Fraction that dimerised, x = (0.00375141 – 0.00354904) / 0.00375141 = 0.053945

  But the answer is 0.108! (No working provided)

  Thanks for answering!!!

   

  For the 1st qn, let X be the % of C12. Then (X/100)(12)+((100-X)/100)(13) = 12.2 and solve for X.

  For the 2nd qn, the number of moles when using PV=nRT is the total number of moles of both gaseous species (ie. both the monomer and the dimer).

  2GaCl3 <---> Ga2Cl6

  Initial : 0.00375141 and 0

  Change : -2X and +X

  Equilibrium : (0.00375141 - 2X) and X

  Total moles of gaseous species = (0.00375141 - 2X) + X = 0.00354904 (from PV=nRT)

  Solve for X.

• Myblazee

  26 Jun 13, 22:23

  help regards accounting home work..

   

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