PHA 327  Exam 2  Disperse Systems 4
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The velocity of sedimentation has what units?
Cm/sec

What is the velocity of sedimentation proportional to?
The Diameter ^2 and g (acc. Due to gravity)

The diameter of the particle to the second power and the acceleration due to gravity are proportional to what other component of sedimentation?
The velocity of sedimentation

What process can be used for separation of colloidal particles?
Ultracentrifugation

Define osmotic pressure:
The pressure to be applied to a pure solvent to prevent it from passing into a solution by osmosis

What is viscosity?
The measure of resistance to liquid flow

What is the unit of viscocity?
Centipoise (cPs)

What characteristic is measured in centipoise (cPs)?
Viscosity

What are the three examples of liquids that exhibit Newtonian flow given in class?
 Glycerin
 Water
 Ethyl Alcohol

Glycerine, Ethyl Alcohol and Water all exhibit what type of flow?
Newtonian

What is Newtonian flow?
Rate of Shear is linearly related to Shearing stress

What type of NonNewtonian flow exist?
 Plastic
 Pseudoplastic
 Dilatant

What example was given in class of a liquid that displays plastic flow?
Flocculated particles in suspensions

Flocculated particles in suspensions exhibit what type of flow?
Plastic (NonNewtonian)

Describe Plastic flow:
 Viscosity decreases with increasing rate of shear
 Elastic fluid until it meets the yield value then it exhibits Newtonian Flow

What type of flow has decreasing viscosity with increasing rate of shear and behaves like an elastic fluid before reaching a yield value, after which it behave Newtonian?
Plastic Flow

What is stokes equation?
 v =velocity of sedimentation (cm/sec)
 d =diameter of the particle
 n =viscosity of the medium
 g =acceleration due to gravity
 δp =density of the particle
 δo =density of the medium

The settling of particles can be described by what equation?
Stokes

Stoke equation describes what?
The sedementation of particles

What is the equation for Diffusion?
 D = Diffusion coefficient
 R = Gas constant
 T = Absolute temp
 η = Viscosity of the solvent
 r = radius of the particle
 N = Avogadro’s number
 M = Molecular weight of the colloidal particle
 ῡ= partial specific volume