1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Liquids and surface tension

  1. Oct 23, 2011 #1
    1. The problem statement, all variables and given/known data

    cphenol/mole dm−3 0.05 0.08 0.127 0.268 0.496
    γ/mN m−1 67.88 64.60 60.10 51.58 44.97

    Estimate the relative surface excess concentrations of phenol in the concentration
    ranges of (i) 0.05 to 0.08 mole/dm3 and (ii) 0.268 to 0.496 mole/dm3 at
    the surface of an aqueous solution from the following data taken at 293 K
    Given that the cross section of a phenol molecule is about 0.4 nm2 estimate
    what fraction of the surface is covered by phenol at the higher of the two
    concentration ranges.


    2. Relevant equations
    dγ = − ΓRTd ln c, where lambda is the surface excess concentration of phenol relative to that of water, gamma is the surface tension, and c the concentration of phenol
    the surface excess concentration of component phenol equals the number of moles of surface excess quantities divided by the surface area



    3. The attempt at a solution
    Basically I worked out the first question, getting answers of 2.8E-6 mol/m^2 and 4.41E-6 mol m^-2, but I have little idea on how to answer the last question. I tried to work backwards, I'm guessing it has something to do with working out the number of moles of phenol per m^2 of the surface and multiplying by the surface area of a phenol molecule, but I'm not sure how to calculate that, and I'd be grateful if you give a hint in the right direction.
     
  2. jcsd
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?