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I am a college student and for my chemistry of solutions class, I had a lab where we had to titrate orange juice to check the calcium content. However, the experimental results are 20% off the labelled calcium content, and in my report I have to provide a "Tentative explanation of the discrepancy."

Is it possible that the orange juice was not completely homogeneous? What I mean is that maybe some of the calcium and other 2+ ions were not well mixed and there were more/less in our sample. Is that possible or are ions always equally dispersed throughout the solvent when in solution?

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    $\begingroup$ Well, I do not remember homogenous orange juice. Were you supposed to determine the total, or dissolved calcium ? What was the procedure ? $\endgroup$ – Poutnik Apr 1 at 15:47
  • $\begingroup$ We had to titrate the solution with an acidic solution (EDTA), a pH buffer and an indicator. The EDTA would react with 2+ ions first, and then with the indicator. $\endgroup$ – Thibaut B. Apr 1 at 16:33
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The calcium amount may change from one fruit to the next one, or from one day to another one, or from one field to another one. 20 % is not a significant difference between such a measurement and another one. And this may happen for any constituant, not specially for calcium.

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  • $\begingroup$ As somewhat of a side note, the FDA must have some tolerance around how much the actual value can vary from the stated value on the label. $\endgroup$ – MaxW Apr 1 at 18:33

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