May 20, 2019, 07:16:06 PM
Forum Rules: Read This Before Posting

Topic: Calculation of diffusion coefficient.  (Read 1339 times)

0 Members and 1 Guest are viewing this topic.

sun725

• Regular Member
• Posts: 72
• Mole Snacks: +1/-0
Calculation of diffusion coefficient.
« on: October 29, 2018, 06:16:49 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.

Borek

• Mr. pH
• Deity Member
• Posts: 24994
• Mole Snacks: +1640/-395
• Gender:
• I am known to be occasionally wrong.
Re: Calculation of diffusion coefficient.
« Reply #1 on: October 29, 2018, 07:14:16 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
Chembuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info, PZWT_s1

sun725

• Regular Member
• Posts: 72
• Mole Snacks: +1/-0
Re: Calculation of diffusion coefficient.
« Reply #2 on: October 29, 2018, 07:16:50 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?

mjc123

• Chemist
• Sr. Member
• Posts: 1574
• Mole Snacks: +225/-9
Re: Calculation of diffusion coefficient.
« Reply #3 on: October 30, 2018, 05:35:05 AM »
Assuming your answer is right, what do you get if you convert the units to cm2 min-1?