Physical Pharmacy Semi-Finals Quiz

Equilibrium Solubility

• Equilibrium solubility can be altered by changing external conditions, such as temperature.
• Solutions with more solute than the equilibrium solubility are unstable.
• Cooling a solution typically leads to crystallization of excess solute.

Unsaturated Solutions

• These solutions contain less solute than the maximum amount that can dissolve at a given temperature.
• Additional solute can still dissolve in unsaturated solutions.

Factors Affecting Solubility

• pH of Solutions:

  • Many drugs are weak acids or bases; their solubility often depends on the pH of the medium.
  • Ionized drugs are generally more soluble in aqueous environments than their unionized forms.

• Nature of Solute and Solvent:

  • The principle "Like dissolves like" applies; polar solutes dissolve in polar solvents, while non-polar solutes favor non-polar solvents.

• Pressure:

  • For gases, increased pressure boosts solubility, as described by Henry's Law.

• Temperature:

  • Usually, solubility increases with temperature, except for gases, where it commonly decreases.

• Particle Size:

  • Smaller particles have larger surface areas which can enhance dissolution rates and solubility.

• Presence of Salts:

  • Salting Out: Presence of salts can decrease solubility.
  • Salting In: Inclusion of salts can occasionally enhance solubility.

Types of Solutions

• Saturated Solutions:

  • No additional solute can dissolve at specific temperature and pressure. Represents the maximum solute concentration.

• Supersaturated Solutions:

  • Contains more solute than what can typically dissolve; these are metastable and can precipitate excess solute.

Components of Solutions

• Solute:

  • The substance that is dissolved (e.g., drugs, salts).

• Solvent:

  • The medium that dissolves the solute (commonly water in pharmaceuticals due to biocompatibility).

Dissolution

• Describes the transfer of molecules from a solid state into solution, often evaluated through the Noyes-Whitney Equation.

Classifications of Dispersed Systems

• Molecular Dispersion (True Solutions):

  • Composed of components with particle sizes less than 1 nm (e.g., oxygen, glucose).

• Colloidal Dispersion:

  • Intermediate particle size (1 nm to 0.5 μm), examples include colloidal silver.

• Coarse Dispersion:

  • Larger particles (>0.5 μm) such as grains of sand and red blood cells.

Properties of Colloids

• Optical Properties:

  • Exhibit the Faraday-Tyndall Effect, scattering light and altering its polarization.

• Kinetic Properties:

  • Show Brownian motion where colloidal particles move continuously, demonstrating diffusion until equilibrium is achieved.

Test your knowledge on equilibrium solubility and the effects of various conditions like temperature on solute dissolution. This quiz is designed for 2nd-year BS Pharmacy students at Arellano University during their semi-finals. Prepare to deepen your understanding of physical pharmacy concepts relevant to real-world applications.