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Why filter a Nearly Saturated Solution of Ca(OH)2

  1. Mar 3, 2009 #1
    From a lab I am about to do:

    "Pour 25.0 mL of nearly saturated solution of Ca(OH)2 into filter paper"

    I am wondering why I would need to filter the solution (what a filter paper would capture). Isn't filter paper just good for removing solids. It is not even expected that all solution will pass through, only 15-20 mL. Why?
  2. jcsd
  3. Mar 3, 2009 #2


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    How are you expected to treat or handle the filtered solution? My guess is that you are filtering any calcium carbonate and want to take actions to prevent any calcium carbonate from forming in the filtered solution.
  4. Mar 3, 2009 #3
    But why would filter paper separate out a dissolved substance? Don't filters just block solids or something?
  5. Mar 3, 2009 #4


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    Yes, that'd normally be the point.

    It's natural that you're going to loose some solution in the process of filtering. Wetting the filter.
    It'd be easier to say what the exact purpose was if we knew the context. But my best guess on the information given is that since it's near-saturated you're trying to get rid of any eventual remaining undissolved calcium hydroxide.
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