da_prospect_2006 S asked:


In the United States, alcohol is rated according to “proof” which is usually defined as twice the percent by volume of pure ethanol in solution, measured at 60*F. What is the molarity of ethanol in a “92 proof” solution of ethanol in water. The density of ethanol (C2H5OH, molar mass=46g/mole) is 0.80g/cm^3 at 60*F; the density of water (H2O, molar mass= 18g/mole) is 1.0 gm/cm^3 at 60*F(15.5*C) Please Explain

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1 Comment so far

1. reb June 18, 2009 9:12 pm

   92 proof is 46% by volume. So let’s assume you have 1,000 mL of mix. So you have 460 ml of ethanol and 540 ml of water.

   calculate the mass of ethanol

   (460)(0.80) = grams of ethanol

   Convert to moles by dividing by 46 g /mol

   SInce it is 1 liter, this is also the molarity

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