Podcast
Questions and Answers
What is the term for the process when molecules or ions move from a solid to a solution?
What is the term for the process when molecules or ions move from a solid to a solution?
The saturation concentration (Cs) is the maximum concentration of a solute that can dissolve in a solvent.
The saturation concentration (Cs) is the maximum concentration of a solute that can dissolve in a solvent.
True
What does the Noyes-Whitney equation estimate?
What does the Noyes-Whitney equation estimate?
Dissolution rate of pharmaceutical particles
According to Fick's Law, the rate of change in solute concentration is directly proportional to the concentration difference across the _____.
According to Fick's Law, the rate of change in solute concentration is directly proportional to the concentration difference across the _____.
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Match the variables with their descriptions in the dissolution equation.
Match the variables with their descriptions in the dissolution equation.
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If the concentration in the bulk solution (C2) is less than the saturation concentration (Cs), what occurs?
If the concentration in the bulk solution (C2) is less than the saturation concentration (Cs), what occurs?
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Crystallization occurs when the concentration of solute in the bulk solution is higher than the saturation concentration.
Crystallization occurs when the concentration of solute in the bulk solution is higher than the saturation concentration.
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Which law describes the dissolution process in terms of concentration change over time?
Which law describes the dissolution process in terms of concentration change over time?
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The rate of mass transfer of solute is inversely proportional to the _____.
The rate of mass transfer of solute is inversely proportional to the _____.
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Which factor does NOT affect the rate of dissolution according to the Noyes-Whitney equation?
Which factor does NOT affect the rate of dissolution according to the Noyes-Whitney equation?
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Study Notes
Dissolution
- The transfer of molecules or ions from a solid to a solution is called dissolution.
- Dissolution is controlled by the relative affinity between the solid and the solvent.
- The extent of dissolution under specific conditions is the solubility of the solute in the solvent.
Solubility
- Solubility is the amount of solute that passes into solution when equilibrium is reached between the dissolved and undissolved solute.
Dissolution Process
- Dissolution begins when particles are small enough to enter the solution.
- Dissolution continues until the solute is completely dissolved.
- The rate of diffusion follows Fick's Law of Diffusion.
Fick's Law of Diffusion
- Fick's Law states that the rate of change in solute concentration over time is directly proportional to the concentration difference across the diffusion layer.
- The equation for Fick's Law is: $\frac{dC}{dt} = kAC$
- Where:
- C = solute concentration at a given point and time
- t = time
- k = rate constant
- A = area
- C = concentration
Dissolution Rate
- When a solid dissolves in a liquid, the concentration difference (ΔC) is the difference between the concentration at the solid surface (C1) and the bulk solution (C2).
- At equilibrium, the solution in contact with the solid will be saturated (concentration = Cs).
- If C2 is less than the saturation concentration, molecules move from the solid into the bulk solution (dissolution).
- If C2 is greater than the saturation concentration, molecules move from the bulk solution to the solid surface (crystallization).
Noyes-Whitney Equation
- The Noyes-Whitney equation describes the dissolution rate from a single spherical particle.
- This equation is useful for estimating the dissolution rate of pharmaceutical particles.
- The rate of mass transfer (dm/dt) of solute molecules or ions through a static diffusion layer is directly proportional to:
- The available area for migration (A).
- The concentration difference across the boundary layer (ΔC).
- The rate of mass transfer (dm/dt) is inversely proportional to the boundary layer thickness (h).
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Description
Test your understanding of the processes of dissolution and solubility. This quiz covers the fundamental principles, including Fick's Law of Diffusion and the conditions affecting solubility. Perfect for students studying chemistry and related sciences.
