Solution To The Boiling Point Problem

1. What is the boiling point of a solution of a non-electrolyte ethylene glycol which is .05 m in water. The Kb = 0.512 C/m.

2. If we used .05 molal solution of Na2SO4 what would be the boiling point?

Solution To Part 1

  1. Plug in the given molal concentration and the Kb into the boiling point elevation equation.

    Tb - 100 = (0.512)(.05) = 0.0256

    Tb = 100 + 0.0256 = 100.0256 C

Solution For Part 2

  1. Write the dissociation equation for Na2SO4

    Na2SO4 + H2O ----> 2 Na+ (aq) + SO4-2 (aq)

  2. Calculate the i factor

    i = sum of coefficients on the right side / coeff of solute on left side = 2 + 1 / 1 = 3

  3. Calculat the Boiling point of the solution using the boiling point elevation equation for an electrolyte.

    Tb - Tb0 = i Kb m = (3)(0.512)(.05) = 0.0768

    Tb = 100 + 0.0768 = 100.0768 C

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    R. H. Logan, Instructor of Chemistry, Dallas County Community College District, North Lake College.

    Acknowledgements:

    Acknowledgements

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    All textual content copyrighted (c) 1997
R.H. Logan, Instructor of Chemistry, DCCCD
All Rights reserved

    Revised: 2/26/97

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