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Titration problems

  1. Mar 12, 2013 #1
    I am doing titration of NaOH with oxalic acid at school and none of my results are close together at all.

    I got
    1. 26.6 mL
    2. 27 mL (although I want to discount this since I wasn't very careful with this)
    3. 25.5 mL
    4. 26 mL
    5. 25.3 mL (For this titration I realized that there was some insoluble material at the bottom of my conical flask. Thus I wanted to discount this as well for possible risk of contamination)

    Can someone explain any possible reasons for such large discrepancies? I have been very careful washed all my equipment etc. but still got bad results.
     
  2. jcsd
  3. Mar 12, 2013 #2

    Borek

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    Staff: Mentor

    Hard to say anything. At least please describe the procedure you are following.
     
  4. Mar 12, 2013 #3
    It's just a simple titration. Measure 25 mL of NaOH solution (with unknown concentration) using a pipette and titrate it using 0.05M oxalic acid.
     
  5. Mar 12, 2013 #4

    Borek

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    Staff: Mentor

    OK, judging from your description you didn't use any indicator to determine the end point. In such a case I am quite surprised your results are that consistent.
     
  6. Mar 12, 2013 #5
    No I used phenolphthalein indicator. I thought in titration's it's kind of expected that an indicator will be used;hence didn't mention it in my previous post.
     
  7. Mar 12, 2013 #6

    Borek

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    Staff: Mentor

    Different indicators will yield different results, so it is a crucial information.

    Was this procedure suggested to you? Titrating oxalic acid with NaOH against phenolphthalein makes sense, but the reverse titration is a rather unorthodox idea, especially taking into account possible contamination of NaOH with carbonates. Effectively that would mean titration of a weak base with a weak acid, which never yields sharp end points.
     
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