Register to reply

Average diameters of colloids

by kasse
Tags: average, colloids, diameters
Share this thread:
Jan22-09, 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.
Phys.Org News Partner Science news on
'Office life' of bacteria may be their weak spot
Lunar explorers will walk at higher speeds than thought
Philips introduces BlueTouch, PulseRelief control for pain relief
Jan23-09, 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.

Register to reply

Related Discussions
Particle Drag in colloids Materials & Chemical Engineering 1
Colloids solid or liquid? Chemistry 7
Voltammetry of alkylated colloids Chemistry 3
Elasticity in colloids (gels, jellies) Introductory Physics Homework 1
Elasticity in colloids (gels, jellies) General Physics 0