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Concentration Citric Acid in Lemon Juice?

  1. Apr 20, 2005 #1
    Hey there ppl!
    I am doing an Acid/Base Titration to investigate whether the concentration of citric acid lemon juice, change over a period of 5 days. So i kindda need some help in this experiment, cause we are not allowed to ask our teacher any help! The main purpose of this experiment is that to see if we can do an experiment without any inputs from our teacher. So i had to come up with my own method and do my own experiment, and plus no one in our school can do the same experiment, so therefore we can't compare out results with anyone else.

    So my questions are:

    1. Will the concentration of citric acid actually varies over a period of 5 days?
    My Answer : Nope, it won't vary, cause a period of 5 days is too less

    2. What are the average titre values for this experiment, when 0.2 M of NaOH is in the burette, and 60 ml of diluted lemon juice is in the conical flask?
    My answer: The values i got were around 23.1-23.8

    These are my answers, can someone here check my answer if you guys have done this experiment?

    I never got a Not Achevied in my entire chemistry assessment, so i don't want to fail this one, Only 3 ppl out of my whole country got an Excellence for this experiment, so i am really scared about passing with an Excellence. Can someone here help me please?
  2. jcsd
  3. Apr 21, 2005 #2


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    Staff: Mentor

    My comment: 3% error in titration is a lot.

    1st answer seems logical to me. Citric acid is rather stable. The question is if the citric acid is the only acidic substance present in the juice and if these other substances (if they exist - I have no idea) - are stable too.

    But I will start with the asumption that it is citric aicd only.
    Last edited by a moderator: Aug 13, 2013
  4. Apr 21, 2005 #3
    The devil is in the details. Think about the equilibriums, they can be expressed as concentration ratios or rate constant ratios. So how long does it take to obtain the equilibrium ?
  5. Apr 21, 2005 #4


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    Staff: Mentor

    I don't get you. Could you elaborate?
    Last edited by a moderator: Aug 13, 2013
  6. Apr 21, 2005 #5


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    Homework Helper

    all in all, the most important thing is your experimental setup. Hint: you'll need a lot of lemons

    you'll also need to be familiar with basic statistical analysis. However this may be a bit too much at your level.

    In general you'll probably need to take lemons of the same size and roughly the same citric acid content (pH) and determine the citric acid content over the 5 days, each day working with a set of lemons.

    You'll need to understand why citric acid exist in a lemon, the biology of it all and I'm not quite sure if this will be very interesting.
  7. Apr 21, 2005 #6
    Sorry I misread your question. I was thinking of something totally different. my bad
  8. Apr 21, 2005 #7
    Hey there Guys!

    Well yeah i am assuming that all the acid in lemon are citric acid, I know there maybe other acids persent in lemon, but i don't care about them, i am only ineterested about citric acid, and i will state it in my Evaluation & Limitation that i assumed that the only acid present in lemon juice in citric! This will give me something to write under the Evaluation part!

    Yeah even my dad was saying something about taking the same size lemon and with the same amount of acid, but i did my experiment with Pure Lemon Cordial, i added 20 mL of the Lemon cordial and 80 mL of water and diluted the cordial. The bottle told me that for every 1 part of lemon i should add 4 parts of water, so the dilution factor was easy to calculate. The reason why i did this was, if i didn't add water, no one can drink the lemon cordial cause its too strong, and the burette readin will under 10mL, and we were instructed not to get any results under 10mL!

    Now my first answer doubt is cleared. Many people that i know from other schools has also agreed that the concentration won't change too much, it will be quite constant. But i need a idea of values for my 2nd question. Does anyone know?

    Thank You so much for replying and helping me out ppl!
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