Crystal Formation Methods

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What is the reason for the formation of crystals during homogeneous nucleation and growth?

The rate of precipitation increases suddenly
The extent to which the ions are soluble decreases when the pH changes in the right direction (correct)
The material that precipitates becomes more soluble
The solvent begins to evaporate rapidly

What is the result of evaporation on the solution?

An increase in the availability of solvent for the ions
No change in the solvent availability
A state of undersaturation
A state of super saturation (correct)

What is the advantage of very careful crystallization?

It is a cheap method of crystallization
It is the best method of preparing materials that are extremely pure (correct)
It produces crystals quickly
It produces crystals of varying purity

What is the phenomenon where compounds can crystallize with different crystal structures?

Polymorphism (D) Signup and view all the answers

What is the importance of polymorphism in industrial manufacturing?

It is a major issue in industrial manufacturing (B) Signup and view all the answers

What is the primary driving force for drying in convective or direct drying?

Reduced air relative humidity (A) Signup and view all the answers

What is the limitation of applying high temperatures in convective or direct drying?

Product quality considerations (D) Signup and view all the answers

What is affected by the rate of precipitation?

The purity of the crystal (A) Signup and view all the answers

What is the purpose of reducing pressure in supercritical drying?

To lower the boiling point (B) Signup and view all the answers

What is the advantage of freeze drying in preserving biological properties?

It retains vitamins and bioactive compounds (C) Signup and view all the answers

What is the characteristic of natural air drying?

It takes advantage of unheated forced air (A) Signup and view all the answers

What is the consequence of using too hot air in convective or direct drying?

Crust formation or case hardening (A) Signup and view all the answers

What is the primary reason why evaporation occurs faster in areas of less pressure?

There is less exertion on the surface, allowing molecules to escape (D) Signup and view all the answers

What is the effect of a larger surface area on the rate of evaporation?

It increases the rate of evaporation (B) Signup and view all the answers

What is the relationship between the density of a substance and its rate of evaporation?

Higher density results in slower evaporation (C) Signup and view all the answers

What is required for boiling to occur?

A combination of heat and reduced pressure (D) Signup and view all the answers

What happens when molecules collide during the evaporation process?

Energy is transferred and the molecules may gain enough to escape (C) Signup and view all the answers

Why don't the molecules in a glass of water typically turn into vapor quickly?

They lack the energy to escape (D) Signup and view all the answers

What factors need to be considered when devising a strategy for drying grains?

Air temperature, relative humidity and moisture content (B) Signup and view all the answers

What is the typical result of increasing the internal energy of a solid substance?

A rise in its temperature to its melting point (B) Signup and view all the answers

What is the term for a substance that has undergone a complete phase change from solid to liquid?

Molten (B) Signup and view all the answers

What is the relationship between the melting point and freezing point of a pure crystalline solid?

The melting point is often equal to the freezing point (B) Signup and view all the answers

What is the effect of increasing pressure on the melting point of a substance?

It lowers the melting point (C) Signup and view all the answers

What is the relationship between the strength of intermolecular forces in a crystal and its melting point?

Weaker forces result in a lower melting point (D) Signup and view all the answers

What is viscosity a measure of in a fluid?

Its resistance to deformation at a given rate (C) Signup and view all the answers

What did Isaac Newton postulate about the shear stress between layers in a fluid?

It is directly proportional to the velocity gradient (A) Signup and view all the answers

Why is close temperature control essential in viscosity measurements?

To ensure accurate measurements of lubricants (D) Signup and view all the answers

What happens to the viscosity of a liquid as its temperature increases?

It decreases (D) Signup and view all the answers

What happens to the viscosity of a gas as its temperature increases?

It increases (C) Signup and view all the answers

What happens to the cohesive forces between molecules in a liquid as it is heated?

They decrease (D) Signup and view all the answers