Calculate the rate of dissolution (dm/dt) of relatively hydrophobic drug particles with a surface area of 2.5×103 cm2 and saturation solubility of 0.35 mg/ml at 25°c in water. the diffusion coefficient is 1.75×10-7 cm2/s, and the thickness of the diffusion layer is 1.25m. the concentration of the drug in the bulk solution is 2.1×10-4 mg/ml.

Explanation:

We can use the Noyes-Whitney equation to calculate the rate of dissolution.

Data:

D = 1.75 × 10⁻⁷ cm²s⁻¹

A = 2.5 × 10³ cm²

Cₛ = 0.35 mg/mL

C = 2.1 × 10⁻⁴ mg/mL

d = 1.25 µm

Calculations:

Cₛ - C = (0.35 - 2.1 × 10⁻⁴) mg·cm⁻³ = 0.350 mg·cm⁻³

d = 1.25 µm = 1.25 × 10⁻⁶ m = 1.25 × 10⁻⁴ cm

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