Crystal Formation Methods
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Questions and Answers

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?

    <p>Polymorphism</p> Signup and view all the answers

    What is the importance of polymorphism in industrial manufacturing?

    <p>It is a major issue in industrial manufacturing</p> Signup and view all the answers

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

    <p>Reduced air relative humidity</p> Signup and view all the answers

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

    <p>Product quality considerations</p> Signup and view all the answers

    What is affected by the rate of precipitation?

    <p>The purity of the crystal</p> Signup and view all the answers

    What is the purpose of reducing pressure in supercritical drying?

    <p>To lower the boiling point</p> Signup and view all the answers

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

    <p>It retains vitamins and bioactive compounds</p> Signup and view all the answers

    What is the characteristic of natural air drying?

    <p>It takes advantage of unheated forced air</p> Signup and view all the answers

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

    <p>Crust formation or case hardening</p> Signup and view all the answers

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

    <p>There is less exertion on the surface, allowing molecules to escape</p> Signup and view all the answers

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

    <p>It increases the rate of evaporation</p> Signup and view all the answers

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

    <p>Higher density results in slower evaporation</p> Signup and view all the answers

    What is required for boiling to occur?

    <p>A combination of heat and reduced pressure</p> Signup and view all the answers

    What happens when molecules collide during the evaporation process?

    <p>Energy is transferred and the molecules may gain enough to escape</p> Signup and view all the answers

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

    <p>They lack the energy to escape</p> Signup and view all the answers

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

    <p>Air temperature, relative humidity and moisture content</p> Signup and view all the answers

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

    <p>A rise in its temperature to its melting point</p> Signup and view all the answers

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

    <p>Molten</p> Signup and view all the answers

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

    <p>The melting point is often equal to the freezing point</p> Signup and view all the answers

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

    <p>It lowers the melting point</p> Signup and view all the answers

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

    <p>Weaker forces result in a lower melting point</p> Signup and view all the answers

    What is viscosity a measure of in a fluid?

    <p>Its resistance to deformation at a given rate</p> Signup and view all the answers

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

    <p>It is directly proportional to the velocity gradient</p> Signup and view all the answers

    Why is close temperature control essential in viscosity measurements?

    <p>To ensure accurate measurements of lubricants</p> Signup and view all the answers

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

    <p>It decreases</p> Signup and view all the answers

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

    <p>It increases</p> Signup and view all the answers

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

    <p>They decrease</p> Signup and view all the answers

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