PHA 327 - Exam 2 - Disperse Systems 5

Home

Get App

Create

What type of Colloid dispersion can tolerate a moderate amount of electrolytes without coagulating or precipitating?

Lyophilic
What is salting out?

When the addition of sufficient amount of electrolytes to a colloid solution can cause agglomeration and sedimentation
Lyophilic colloid dispersion cannot tolerate electrolytes (T/F)?
- False, they can tolerate a moderate amount of electrolytes
- When too large a quantity of electrolytes is added to the dispersion, salting out occurs
What type of Colloid dispersion is not thermodynamically stable?

Lyophobic colloid
The precipitating power that an electrolyte exerts on a colloid dispersion is based on what characteristic?

The valence of the ion
What does the addition of a small amount of electrolyte to a Lyophobic colloid dispersion achieve?

Stabilization by providing a charge to the particles
How would you stabilize a Lyophobic colloid dispersion?

Add a small amount of electrolyte
Calcium and Barium are more or less effective at precipitating an arsenious sulfide solution than Sodium and Potassium?
- They are more
- Calcium and Barium are divalent and Sodium and Potassium are Univalent
Why are Calcium and Barium more effective at precipitating an arsenious sulfide solution than Sodium and Potassium?
- Precipitating power of an electrolyte depends on the valence of the ion
- Calcium and Barium are divalent and Sodium and Potassium are Univalent
What is the Gold Number?

mg of dry hydrophilic substance required to prevent a color change from red to violet in a Gold solution after adding 1mL of 10% NaCl
What does a color change from red to violet when testing for the gold number indicate?

A partial flocculation
How could you determine the molecular weight of a colloid by its dispersion properties?

By measuring light scattering
Why would you m measure light scattering properties of a colloid dispersion?

To determine the molecular weight of a colloid
What is the Tyndall effect?

When a light beam passes through a colloid dispersion and observed from a right agle, it appears cloudy
What is Brownian motion?

Random movement of particles in dispersion due to collisions
What is diffusion?

The movement of particles from areas of high concentration to areas of low concentration, to establish equilibrium
Describe a Lyophobic Colloid:
- Repulsion of the dispersion medium
- Hydrophobic
Describe an Association Colloid:

Contains both polar and non-polar components (Amphiphilic)
Are hydrophobic or hydrophilic colloidal dispersion easier to prepare?

Hydrophilic
What are the three methods for Preparing a hydrophobic colloidal dispersion:
- Colloid mills and Ultrasonification
- Condensation method
- Dispersion method
What is the Condensation method?
- A method for preparing a hydrophobic colloid dispersion
- It is achieved by a high frequency alternating current that is passed through a solvent
What is the Dispersion Method?
- A method for preparing a hydrophobic colloid solution
- It is achieved by Mechanical and electrolytic disintegration
Why would you use a Colloid mill, ultrasonification, the condensation method or the dispersion method?

To prepare a Hydrophobic colloid solution
Why is it important to remove as many dissolved ions from a colloid solution as possible?

Presence of electrolytes in a colloid dispersion precipitates the colloid
What material can cause the colloid to precipitate?

Electrolytes
What two ways can purification of a colloid dispersion be achieved?
- Ultrafiltration
- Dialysis
Why would you perform ultrafiltration or dialysis of a colloid dispersion?

To purify the colloid dispersion of electrolytes that may precipitate the colloid
What type of colloids are thermodynamically stable?

Lyophilic and Association Colloids

Author

kyleannkelsey

214932

Card Set

PHA 327 - Exam 2 - Disperse Systems 5

Description

PHA 327 - Exam 2 - Disperse Systems 5

Updated

2013-04-22T01:20:17Z

Show Answers