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Homework Help: Molarity of a solution of ethanol in water

  1. Jan 11, 2007 #1
    Calculate the molarity of a solution of ethanol in water,in which the mole fraction of ethanol is 0.040.
    Can anyone help me to solve this problem?:bugeye:
  2. jcsd
  3. Jan 11, 2007 #2
    i think

    Then the mole fraction of water is 0.96...so the solution is 96% water and 4%Ethanol...this shoule help you going if you were unsure what the fraction was.

    Molarity= Moles of Solute / litres of solution

    Mole fraction (Ethanol) = Moles of Ethanol/ Moles of Ethanol + Water

    So do you know how many Litres or are you just going to assume?

    So if we use a basis of 100 moles.....96 moles are water and 4 moles are ethanol and assume 150 litres


    molarity = 4 moles /150 litres = 0.0266
  4. Jan 12, 2007 #3
    Thanks for helping me...............:)
  5. Jan 14, 2007 #4


    User Avatar

    Staff: Mentor

    Only in terms of moles, stating it this way may sound like you are suggesting this solution is just 4% w/w ethanol - which is not true (it is 9.6% w/w).

    It will be better said that such solution contains 4 moles of ethanol per every 96 moles of water.

  6. Jan 16, 2007 #5
    No..i said mole fraction not w/w
  7. Jan 16, 2007 #6
    I know what you mean though....
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