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Homework Help: Investigating the loss of nitrogen as urea from the body.

  1. May 6, 2008 #1


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    1. The problem statement, all variables and given/known data

    I am required to plan an investigation to find out how changes in the consumption of protein in the diet influences the excretion of urea in humans.

    • 10g per 100cm3 (10%) solution of urea.
    • Urease tablets or 5g per 100cm3 (5%) solution of urease
    • 0.1moldm-3 hydrochloric acid
    • pH indicators e.g. litmus paper ect
    • School/ laboratory resources

    2. Relevant equations

    I have been told that urea + water and urease makes ammonium carbonate and that I can use titration to find the concentration of urea.

    3. The attempt at a solution

    I am going to use titration on various known concentrations of urea to make a calibration curve that can then be used on real urine samples.

    Q. Will making a calibration curve be of any use to people that are hoping to carry out the experiment as they would surley have to carry out titration anyway and therfore would have not much need to use the calibration curve as they will have practically done the whole thing themselves anyway?
  2. jcsd
  3. May 6, 2008 #2


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    Based on a theoretical perspective some of the carbonate may become carbon dioxide and you may need to utilize the proper indicator or perhaps a device which continuously records the titration curve so as to know that the titration pertains to carbonate and not ammonia. Someone else here may be more experienced with this particular experiment.

    I'm not understanding your proposal for a titration based calibration curve - calibration curves are good for spectrophotometric methods if you can conjure one up however your school may or may not have the equipment.
  4. May 7, 2008 #3


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    Google "Kjeldahl Method".
  5. May 7, 2008 #4


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    Nice of you to mention that - according to the Kjeldahl Method it's fine to titrate carbonate with sulfuric acid - the urease method however seems more simplistic yet may not be as accurate as the Kjeldahl Method.
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