60 Questions
Why is mixing considered a fundamental step in most process sequences?
To randomize dissimilar particles within a system
Which term is synonymous with mixing according to the text?
Blending
What is the main purpose of mixing in the context of pharmaceutical products?
To secure uniformity of composition
In the mixing process, what happens to dissimilar particles within a system?
They are randomized
Which of the following is NOT a reason for carrying out mixing in pharmaceutical manufacturing?
To promote segregation
What additional process does agitation during mixing supplement in the context of chemical reactions?
Diffusion
What are the two primary components of a liquid mixing system?
Tank and means of supplying energy
Which component is used to direct the bulk movement of material in mixers?
Ducts
Which type of mixing is usually more feasible for limited volumes of materials?
Batch mixing
How are impellers classified in terms of mixing liquids?
By the type of flow pattern they produce
Which flow pattern is perpendicular to the impeller shaft?
Radial flow
What serves to direct the flow of material within the vessel besides supplying power?
Impellers
What kind of mixing occurs when shear reduces the scale of segregation by thinning dissimilar layers?
Diffusive mixing
How does diffusive mixing by diffusion reduce the intensity of segregation?
By exchanging positions of particles within the powder bed
What equipment is used for rapid overall mixing involving tumbling motion?
Batch Tumblers/Blenders
Which geometric form is NOT mentioned as a type of tumbler blender commercially available?
Pyramid
In a tumbling mixer, what enhances the resulting tumbling motion?
Lifter blades or baffles
What is the main effect of shear occurring between regions of different composition and parallel to their interface?
Reduces scale of segregation
Which type of blender is recommended for precision blending?
Twin-shell blenders
What type of motion is not conductive to efficient mixing in cubical and polyhedron-shaped blenders?
Sliding action
What is a drawback associated with ribbon mixers?
Difficult to clean
What type of motion characterizes the mixing pattern in double cone blenders?
Rolling motion
Which mixer exhibits shearing action between moving blades and trough?
Agitator mixer
What property of powders makes them difficult to mix due to agglomeration?
High forces of cohesion
What is considered as a practical upper limit for the viscosity of materials that can be mixed using turbines or flat blade devices?
10 poise
Which of the following statements is true about mixing thick creams, ointments, and pastes?
They have a high viscosity, making it difficult to generate turbulence within their bulk.
What is a characteristic of turbines or flat blade mixing devices?
They are insensitive to changes in power consumption, density, and viscosity.
In the mixing of two immiscible liquids, what is the primary mechanism involved?
Subdivision of one phase into globules and distributing them throughout the bulk fluid.
What are the two primary forces involved in the mixing of two immiscible liquids?
Interfacial tension and shear forces
How is the selection of mixing equipment determined for low-viscosity systems?
Based on the mechanism by which intense shearing forces can be generated
What type of mixing involves systems where spontaneous, irreversible, and complete mixing would take place by diffusion?
Positive mixing
Which type of mixing is more difficult to form and maintain, requiring a higher degree of mixing?
Negative mixing
What occurs in neutral mixing systems unless acted upon by an external energy input?
Remain static
Forces of shear during fluid mixing are generated by interactions between moving fluids and:
Solid surfaces
What is the derivative of velocity with respect to distance measured normal to the direction of flow known as?
Shear rate
What classification depends on the relationship between shear rates and applied stress for fluids?
Rheological classification
What type of mixer is characterized by the development of a vortex at the center of the vessel?
Impeller mixer
Which fluid mixing device induces tangential flow but does not produce mixing except near the tank walls?
Grid mixer
What is the drawback associated with the formation of a vortex during mixing?
Increased likelihood of foaming
Which device typically includes vanes, baffles, screws, grids, or combinations for efficient mixing?
Impeller mixer
At what viscosity range is the formation of a vortex during mixing considered undesirable?
< 20,000 cps
Which type of flow pattern is characteristic of turbines with blades arranged perpendicular to the impeller shaft?
Radial flow
What is the primary effect of a propeller in mixing liquids?
Producing axial flow
How are turbines distinguished from propellers in terms of blade pitch?
Turbines have blades with varying pitch
Which impeller type induces radial flow by centrifugal action?
Turbines with 90-degree blades
What is a key characteristic of turbines' design that allows operation in highly viscous fluids?
Simple and rugged design
In what type of fluid are propellers most efficient?
Low-viscosity liquids
What type of flow pattern is induced primarily by the setup of propellers?
Axial flow
What type of motion characterizes the mixing pattern in double cone blenders?
Rolling
Which blender type is NOT recommended for precision blending according to the text?
Planetary mixer
What is the drawback associated with ribbon mixers mentioned in the text?
Higher power requirement
Which type of mixing is NOT conducive to efficient mixing in cubical and polyhedron-shaped blenders?
Sliding
What additional mixing action occurs in twin-shell blenders during each revolution?
Agglomeration
What is a common drawback associated with sigma blade and planetary mixers mentioned in the text?
Relatively higher power requirement
What is the practical upper limit of viscosity for the application of turbines or flat blade mixing devices?
15 poise
What type of forces play a role in the mixing of two immiscible liquids?
Surface tension and shear forces
How are high shear rates achieved in low-viscosity systems during mixing?
By passing the fluid under high pressure through small orifices
What is the primary function of a turbine or flat blade design in mixing thick creams and ointments?
Generate turbulence within the bulk
In a polyphase system, what is the effect of the first force on the globules within the fluid?
Maintains globule shape integrity
Which factor influences the selection of equipment for generating intense shearing forces in liquid mixtures?
Viscosity of the liquids
This quiz covers the content of Mixing Chapter 1 in Industrial Pharmacy I, including mixing mechanisms, scale of segregation, equipment selection, solid mixing, and more. Test your knowledge on the importance of mixing in pharmaceutical product manufacturing.
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