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Homework Help: chemistry

Posted by bliss on Friday, January 25, 2013 at 12:18pm.

a sample of compound C,H,N and O with a mass of 0.6216 was found to contain 0.1735g C,0.01455g H,0.2024g N.Its molecular mass 129.calculate its epirical and molecular formulas.

• chemistry - DrBob222, Friday, January 25, 2013 at 4:49pm

  mol = g/molar mass.
  Calculate mols of each element; e.g.,
  0.1735/12 = 0.0145 = mols C.
  Do the same for H and N.
  grams O = 0.6216-(C+H+N)
  mols O = g/molar mass.
  
  Find the ratio of the elements to each other. That gives you the empirical formula. Now find the empirical formula mass and determine molecular formula this way.
  empirical formula mass x factor = molar mass.
  Solve for factor(call that n) and round to a whole number (if it isn't whole to begin with), then the molecular formula is
  (CxHyNzOw)_n
  

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