Biology Forum › Community › General Discussion › Concentrations in Percent (v/v)

last updated by canalon 13 years, 10 months ago
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    • June 17, 2010 at 12:47 am #13448
      cortinator
      Participant

      "Describe how to prepare 50 ml of 75% ethyl alcohol when your only source is a stock container of 95% ethyl alcohol."

      Help! I have no clue what this means.

    • June 17, 2010 at 9:27 pm #100194
      JackBean
      Participant

      the 50 ml contain 0.75*50ml of pure ethanol. This you take from the 95%, so you must divide it by 0.95

    • June 17, 2010 at 9:29 pm #100196
      canalon
      Participant

      Ci x Vi = Cf x Vf
      This is all you need. i stand for initial, f for final.
      So you know the final volume and concentration, and knows the the initial concentration, so plug the numbers and solve for the initial volume.

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