Concentrations in Percent (v/v) - Biology Forum

last updated by

canalon 14 years, 5 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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