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Homework Assignment #11 – Updated October 22, 2018

Posted by biotransport in homework assignments.

Here is HW #11  due on October 29th:

1. A drug has an equilibrium solubility in water of 0.0025 g cm^-3. The diffusivity of the drug in water is 0.9 x 10^-5 cm2/sec. The drug is made into particles that have a radius of 0.1 cm and these particles have a density of 1.27 g/cm^3. These particles are all of the same size and are gently mixed in water in a stirred vessel. Estimate the length of time in hours (hrs) that it will take for these drug particles to completely dissolve. You can assume that the vessel volume is so large that the concentration of the drug in the bulk liquid is very small in comparison to the drug solubility. Also since the particles are all the same size, the time to dissolve is the same for all the particles.

2. How long would it take a small bubble of air (MW=29) to dissolve in water? Assume the initial diameter of the bubble is 2mm and that the ratio of the particle or air bubble density and the saturation concentration of air in water is  50. Also, the diffusivity of air at these conditions is 2 x10^-5 cm^2/sec.

3. In chapter 5, also work problems 13, 29.



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