Lecture 9 – Solid Mixing and Segregation

c

What is the main goal of solid-solid mixing in industry?
A. To compress powders
B. To remove moisture
C. To create a homogeneous distribution of particles
D. To increase particle size

d

Which of the following is NOT a mechanism of solid mixing?
A. Diffusive
B. Convective
C. Shear
D. Absorptive

c

Diffusive mixing is also known as:
A. Macromixing
B. Slip zone mixing
C. Dispersion or micromixing
D. Layered mixing

c

Convective mixing involves:
A. Interchange of individual particles
B. Layer-by-layer flow
C. Interchange of groups of particles
D. Chemical reactions

b

Shear mixing is associated with:
A. Particle sedimentation
B. Mixing layers sliding past one another
C. Homogeneous vapor mixing
D. Free-fall motion

c

Which of the following is essential for effective mixing?
A. Long residence time
B. Uniform humidity
C. Particle size and density control
D. Agglomeration of particles

c

A failure in mixing can lead to:
A. Better energy use
B. Increased product yield
C. Overmixing or product inconsistency
D. Reduced segregation

c

Overmixing may result in:
A. Better mixing quality
B. Agglomeration of fine particles
C. Breakage and fines generation
D. Improved segregation

c

Which term refers to the process of a mixture separating after mixing?
A. Blending
B. Agglomeration
C. Demixing
D. Reconstitution

c

What is a common term for segregation in powders?
A. Homogenization
B. Attrition
C. De-mixing
D. Filtration

d

Which type of segregation occurs when large particles roll to the side?
A. Sieving
B. Fluidization
C. Agglomeration
D. Trajectory

c

Sieving segregation typically affects:
A. Large particles
B. Fine cohesive powders
C. Small particles
D. Liquids

c

Fluidization segregation mostly impacts:
A. Liquids
B. Cohesive solids
C. Fine particles
D. Large granules

d

Agglomeration segregation is prominent in:
A. Coarse powders
B. Metallic solids
C. Free-flowing granules
D. Cohesive fine powders

b

Binary mixing refers to:
A. Mixing of liquid with powder
B. Mixing of two solid components
C. Gas-liquid mixing
D. Three-component blending

c

What is used to quantify mixing in binary systems?
A. Ratio
B. Pressure
C. Standard deviation and variance
D. Mixing time

c

The British Pharmacopoeia (BP) limits variation in ingredient content to:
A. ±1%
B. ±5%
C. ±10%
D. ±15%

b

In the BP standard tablet example, active ingredient was what percentage?
A. 5%
B. 10%
C. 50%
D. 90%

c

Poor mixing can result in:
A. Enhanced product value
B. Lower production cost
C. Product rejection and added cost
D. Better compressibility

c

What does post-mixing difficulty often result in?
A. Stable mixtures
B. Efficient processing
C. Segregation
D. Color change

c

Variance in composition is used to measure:
A. Fluidity
B. Color
C. Homogeneity
D. Solubility

c

The term ‘standard deviation’ in mixing refers to:
A. Particle attrition rate
B. Equipment tolerance
C. Spread in composition after mixing
D. Moisture level

b

A high variance in a powder mix implies:
A. Uniformity
B. Poor mixing
C. Smaller batch size
D. Excessive moisture

c

Binary mixing analysis often assumes particles are:
A. Different sizes
B. Compressible
C. Same size and weight
D. Hollow

b

Which statistical property is most directly related to content uniformity?
A. Mean
B. Variance
C. Mode
D. Range

c

Homogeneity in a sample is improved by:
A. Increasing moisture
B. Reducing mixing time
C. Ensuring adequate mixing mechanisms
D. Using larger particles only

c

In sampling, mixing effects can be evaluated by looking at:
A. Mean only
B. Density profile
C. Distribution of active ingredient
D. Humidity changes

c

Acceptable variability in tablet uniformity is determined by:
A. Flavoring
B. Particle size
C. Regulatory standards
D. Moisture content

b

Sample case studies help evaluate:
A. Fluidization only
B. Mixing and segregation patterns
C. Combustion rate
D. Tablet hardness

c

The use of standard deviation helps compare:
A. Time intervals
B. Color changes
C. Degrees of mixing
D. Mechanical wear

d

A higher number of particles in a sample usually results in:
A. Better variance
B. Reduced precision
C. Lower cost
D. Improved uniformity

c

Sample mass can influence:
A. Mixing force
B. Visual appearance
C. Variability and measurement precision
D. Compression rate

d

If all particles are the same, the sample is assumed to be:
A. Randomized
B. Non-cohesive
C. Fully segregated
D. Ideal

c

For pharmaceutical tablets, active content variation must stay within:
A. ±2%
B. ±8%
C. ±10%
D. ±20%

a

A binary system is considered homogeneous when:
A. Variance is zero
B. All particles are white
C. They settle quickly
D. Density is lowest

b

Deviations in homogeneity may require:
A. Repackaging
B. Remixing
C. Cooling
D. Crystallization

b

What increases the number of particles in a tablet?
A. Adding fillers
B. Reducing particle size
C. Increasing pressure
D. Heating

c

Accurate dosing requires:
A. Soft materials
B. Cohesion
C. Uniform mixing
D. Higher density

c

Mixing failures in pharma can lead to:
A. Improved bioavailability
B. Regulatory approval
C. Dosage inconsistency
D. Longer shelf life

b

Standard deviation is zero in a mix that is:
A. Fully demixed
B. Perfectly mixed
C. Under-mixed
D. Overdosed

c

Which term best describes powders that tend to stick together?
A. Crystalline
B. Agglomerated
C. Cohesive
D. Elastic

b

Van der Waals forces increase significantly as:
A. Particle size increases
B. Distance between particles decreases
C. Temperature rises
D. Mixing time shortens

c

Cohesion due to electron exchange is known as:
A. Van der Waals force
B. Moisture bonding
C. Electrostatic charging
D. Magnetic pull

b

Electrostatic charging in powders occurs when:
A. Particles are frozen
B. Surfaces rub or contact
C. Moisture is removed
D. Materials are compressed

c

Moisture bonding leads to cohesion by:
A. Generating heat
B. Causing oxidation
C. Forming liquid bridges
D. Promoting evaporation

a

Agglomeration due to cohesion typically forms:
A. Dry clusters
B. Liquid pools
C. Gas bubbles
D. Stable solutions

c

Geldart's classification is used to categorize:
A. Cohesive forces
B. Segregation types
C. Powder flowability
D. Particle color

c

The most cohesive powders are generally:
A. Large particles
B. Hydrophobic materials
C. Fine and moist particles
D. Nonpolar solids

b

What is the first theoretical method of dealing with cohesion?
A. Moisture addition
B. High mixing intensity
C. Coating particles
D. Vacuum drying

b

High shear mixing is important in cohesive systems because:
A. It increases bulk density
B. It helps break down clumps
C. It reduces particle count
D. It separates liquid phases

c

A practical method to reduce cohesion is to:
A. Heat the powder
B. Freeze dry
C. Use coating techniques
D. Increase particle size

c

Applying a cohesive powder to a free-flowing powder is a:
A. Shear mixing technique
B. Moisture control method
C. Coating process
D. Precipitation process

c

Which method involves intentionally bonding fine powders to larger particles?
A. Agglomeration
B. Granulation
C. Coating
D. Dispersion

c

The term "slip zone" is associated with:
A. Convective mixing
B. Sieving
C. Shear mixing
D. Moisture binding

c

Segregation due to falling trajectory affects:
A. Fine particles
B. Liquid droplets
C. Large particles
D. Dust particles

b

Side-to-side segregation is also called:
A. Fluidization segregation
B. Trajectory segregation
C. Sieving
D. Shearing

c

When fine particles rise due to air currents, it is called:
A. Sieving segregation
B. Shear segregation
C. Fluidization segregation
D. Dusting

b

Agglomeration segregation is most prominent in powders that are:
A. Highly charged
B. Cohesive and fine
C. Spherical
D. Heat-treated

b

Which segregation type occurs when small particles pass through gaps in a bulk?
A. Agglomeration
B. Sieving
C. Fluidization
D. Trajectory

c

The tendency for segregation increases with:
A. Uniform particle shape
B. Consistent density
C. Large size and density differences
D. Temperature uniformity

c

Which particle property increases susceptibility to fluidization segregation?
A. High density
B. Coarse texture
C. Fineness
D. Irregular shape

c

When segregation occurs during transport, it is mostly:
A. Diffusive
B. Shear-related
C. Trajectory-based
D. Density-driven

b

Preventing segregation after mixing often involves:
A. Reducing airflow
B. Rapid transport and minimal handling
C. Adding water
D. Heating the mix

c

Powders with higher electrostatic charge are:
A. More likely to segregate
B. Less likely to mix
C. More cohesive
D. More lubricated

c

One indicator of poor post-mixing stability is:
A. Homogeneous product
B. Consistent variance
C. Segregation
D. Smooth flow

c

Moisture bridging is most affected by:
A. Ambient noise
B. Dry storage
C. Environmental humidity
D. Surface polish

d

In practice, reducing powder cohesion can involve:
A. Tuning pH
B. Gentle heating
C. Equipment vibration
D. Particle coating

d

What promotes re-agglomeration of powders post-mixing?
A. Long storage
B. Fine particle size
C. Electrostatic buildup
D. All of the above

c

Fine cohesive powders are often pre-treated with:
A. Cooling agents
B. Mixing retardants
C. Flow aids or coatings
D. Antioxidants

b

Shear mixers are effective because they:
A. Vibrate particles apart
B. Provide intense interlayer movement
C. Use vacuum suction
D. Rely on fluid flow

b

Diffusive mixing equipment works primarily through:
A. Vibration
B. Particle-to-particle contact during random motion
C. Compressive action
D. Rotating blades
Answer: B

b

One example of equipment using diffusive mixing is:
A. Paddle blender
B. V-blender
C. Screw conveyor
D. Ribbon mixer

c

Diffusive mixing is ideal for:
A. Sticky wet powders
B. Large-volume liquid slurries
C. Free-flowing powders
D. Dense materials

b

Convective mixing equipment mixes by:
A. Sliding particles
B. Moving groups of particles
C. Crushing powder
D. Melting components

c

Equipment using convection often includes:
A. V-blenders
B. Shaker tables
C. Paddle mixers
D. Sintering ovens

b

Convection mixers are effective for:
A. Gentle, low-volume batches
B. Intensive large-scale mixing
C. Filtration
D. Coating processes

b

Shear mixing equipment introduces mixing by:
A. Blade vibration
B. Layer slipping and force
C. Particle sieving
D. Pneumatic flow

b

An example of a shear mixer is the:
A. Turbula mixer
B. Ribbon blender
C. Fluid bed dryer
D. Static mixer

c

Shear mixers are especially helpful in handling:
A. Dust particles
B. Granules
C. Cohesive powders
D. Liquids

a

Which equipment can perform both convection and shear mixing?
A. Screw extruder
B. Tray dryer
C. Ball mill
D. Jaw crusher

c

Proper selection of mixing equipment depends on:
A. Equipment color
B. Operator experience
C. Powder characteristics and required mixing type
D. Cost of labor

d

The V-blender is shaped like:
A. A U
B. A cone
C. A cylinder
D. A “V”

c

For dry powder blending, the most appropriate mixer is:
A. Agitated tank
B. Fluidized bed
C. Ribbon blender
D. Spray dryer

c

Mixing equipment efficiency is highest when:
A. Overfilled
B. Underloaded
C. Operated near optimum fill level
D. Run intermittently

b

Cohesive powders require which of the following?
A. Diffusive blending only
B. High-intensity shear
C. Vacuum coating
D. Moisture addition

c

One drawback of shear mixing is:
A. Excessive cooling
B. Energy savings
C. Particle breakage
D. Uniformity

c

In free-flowing systems, the best mixing mechanism is:
A. Shear
B. Convective
C. Diffusive
D. Explosive

c

For highly cohesive materials, which method is LEAST effective?
A. Shear mixing
B. Coating
C. Diffusive mixing
D. High-speed blender

c

Equipment that uses a rotating shell for blending is called a:
A. Planetary mixer
B. Ribbon blender
C. Drum blender
D. Cone dryer

c

In binary mixing, the main goal is to achieve:
A. Particle growth
B. Particle destruction
C. Uniform distribution of two solids
D. Wet granulation

b

Segregation post-mixing can be minimized by:
A. Extending mixing time indefinitely
B. Gentle post-mixing handling
C. Pouring from height
D. Adding humidity

c

A variable speed mixer helps control:
A. Temperature
B. Electrostatic force
C. Mixing intensity
D. Particle hardness

c

Sieving segregation is more likely when:
A. Particle size is uniform
B. Powders are sticky
C. Small particles can fall between large ones
D. Equipment is sealed

b

Standard deviation approaches zero when:
A. Segregation increases
B. All components mix perfectly
C. Humidity rises
D. Electrostatic force dominates

b

Which mixing mechanism is most likely to randomize particles quickly?
A. Diffusive
B. Convective
C. Shear
D. Fluidic

b

Mixing intensity depends heavily on:
A. Color
B. Shear force and equipment speed
C. Weight of operator
D. Cooling system

c

Moisture bonding increases with:
A. Lower ambient humidity
B. Increased airflow
C. Moist environment
D. Vibratory motion

c

Which of the following is NOT a mechanism of segregation?
A. Sieving
B. Fluidization
C. Shear
D. Trajectory

a

A mixer that moves powder in multiple axes is a:
A. Turbula mixer
B. Paddle blender
C. Tray dryer
D. Screw feeder

c

Consistent batch mixing results in:
A. High variance
B. Poor homogeneity
C. Uniform product quality
D. Overmixing