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Author Topic: Calculation of diffusion coefficient.  (Read 1285 times)

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sun725

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Calculation of diffusion coefficient.
« on: October 29, 2018, 12:16:49 PM »

I have this task that I had to solve. I am going to translate it as good as I can from the original language:

The diffusion coefficient of Piroxicam in aqueous solution is 5,45*10-10 m2s-1 at 25 C. The Viscosity of water at 25 C and 37 C is respectively 8,91*10-4 Pa s and 6,92*10-4 Pa s

I used the following formulas in order to find the diffusion coefficient:
R=kT/6πηD and got 4,42*10-10 m

Then
D=kT/6πηR and got 7,42*10-10 m2 s-1

However, once checking for my answer I saw that the last answer was correct but they also included this answer: 4,45*10-4 cm2 min-1
How did they achieve this answer? I hope someone can help me.

Thanks in advance!
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Borek

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Re: Calculation of diffusion coefficient.
« Reply #1 on: October 29, 2018, 01:14:16 PM »

The diffusion coefficient of Piroxicam in aqueous solution is 5,45*10-10 m2s-1 at 25 C

Something is off. Not sure what you are calculating if the diffusion coefficient is given
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sun725

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Re: Calculation of diffusion coefficient.
« Reply #2 on: October 29, 2018, 01:16:50 PM »

Forgot this part, I am sorry:
Calculate Piroxicams diffusion coefficient in aqueous solution at 37 C under the assumption that the solubility has the same viscosity as pure water.

Hope it makes sense now?
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mjc123

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Re: Calculation of diffusion coefficient.
« Reply #3 on: October 29, 2018, 11:35:05 PM »

Assuming your answer is right, what do you get if you convert the units to cm2 min-1?
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