In extracting NaCl (sodium chloride) from water, why is it necessary to do this 3 times as opposed to only one

I'm doing a chem experiment and I need to answer these pre-questions before I'm allowed in the lab! We're studying the separation of components of a mixture and apparently we have to extract NaCl from water three times and I have no idea why!?! Any Help would be greatly appreciated.

3 Answers

  • Because each time you extract, you only get ~50% of what was in there. So, after 1 time, you have 50%. The 2nd time, you get 50% of the 50% left from trial 1 (so, 25%) - giving you a total of 75% of the NaCl after 2 extractions. Trial 3 gets 50% of the remaining 25% (which is 12.5%), so after 3 trials, you have extracted ~87.5% of your NaCl. Doing it 4 times only gets you another 6.25%, 5x is an extra ~3% - so on and so forth.

    You do it 3 times to get the maximum extraction for only a few trials. Anything more than 3 or 4 times is not worth the effort for the small yield!

  • It depends on what solvent you're extracting into. However, NaCl is ionic, and strongly prefers to stay with the water. That's probably why you have to do it three times. You will only get some percentage of the NaCl each time.

  • Um trials to compare data obtained?

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