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Homework Help: How to calculate displacement from density?

  1. Aug 10, 2012 #1
    If this the wrong section to post this, please know that I am very sorry, but I don't know much about any of the things going on, on here so please bare with me.

    Say you got some powder, and say this powder has a density of 1.06g/cm3 (or 1.06g/mL, right?).

    Now say you want to put 2500mg of this powder in a solvent mixture (made from cottonseed oil, 0.3mL benzyl alcohol and 1.7mL benzyl benzoate), that you want it to be total of 10ml, with the powder being at a concentration of 250mg/mL

    How would one go about calculating the displacement caused by this powder, which will then determine how much oil one would need to use?
  2. jcsd
  3. Aug 10, 2012 #2
    Simple way of putting it:

    Powder has a density of 1.06g/cm3

    How much will 1000mg of the powder displace 10ml of water
  4. Aug 10, 2012 #3
    If the powder is completely insoluble, and does not form any kind of compounds with water, then the resultant volume is a simple sum of the volume of the powder and of the liquid.

    Otherwise, you will need the properties of the resultant solution/compound.
  5. Aug 10, 2012 #4
    Okay let us say the powder is insoluble, how would one go about calculating thing (I need a formula)
  6. Aug 10, 2012 #5
    Say the concentration is c mg/mL.

    Then in volume V ml of the mixture, you will have m = cV mg of the powder.

    The density of the powder is ρ mg/mL, so mass m corresponds to volume v = m/ρ mL.

    Then the volume of the filler liquid is u = V - v mL.

    I am sure you can substitute and simplify the rest. But mind the units!
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