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Average diameters of colloids 
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#1
Jan2209, 08:17 PM

P: 463

A dispersion of spherical polymer particles contains Np = 4•1013 particles/dm3. The total surface of the particles in 1 dm3 is Asp = 820 m2.
a) What kind of average diameter can we calculate. Calculate this average diameter. b) If we know that the dispersion contains 60 vol% water, we can calculate another type of average diameter. Which? Find it! a) Surface average. [tex]\bar{d_s} = \sqrt{\frac{\Sigma n_i d_i^2}{\Sigma n_i}}[/tex] b) Volume average. [tex]\bar{d_s} = \sqrt{\frac{\Sigma n_i d_i^3}{\Sigma n_i}}[/tex] I don't know how to incorporate the data into the formulas. 


#2
Jan2309, 05:44 AM

P: 19

Can't you just work it out by taking the surface area of a sphere and working back to get the radius?
You know the total surface area of the total particles in 1 litre, and you know how many particles there are in 1 litre, so from that you can work out the surface area of 1 particle. 


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