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### AuthorTopic: How to obtain concentration of a FeG+ using activity coefficient?  (Read 3799 times) !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="https://platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() {var po = document.createElement("script"); po.type = "text/javascript"; po.async = true;po.src = "https://apis.google.com/js/plusone.js";var s = document.getElementsByTagName("script")[0]; s.parentNode.insertBefore(po, s);})();

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#### Chaste

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##### How to obtain concentration of a FeG+ using activity coefficient?
« on: October 27, 2010, 04:43:11 AM »

Equilibria involved :
FeG+ + G-  FeG2 K2 = 3.2 x 103
G- + H2 HG + OH- Kb = 6.0 x 10-5
G- is the amino acid glycine.
Suppose that 0.050 mole of FeG2 is dissolved in 1 litre of water.

Qns: Using activity coefficient, find FeG+ if the pH is fixed at 8.5 and the ionic strength is 0.10M. For FeG+, use gamma = 0.79. and for G- use gamma = 0.782

My attempt at the question:

MBE 1 = 0.05 = [FeG+] + [FeG2]
MBE 2 = [FeG+] = [HG] + [G-]

the ionic strength being 0.1,

0.1 = 0.5 x [FeG+] + [G-] + [H3O+] + [OH-]   ----- 1

and I'm stuck. I suppose I need to solve simultaneous equations. how do I make use of the pH and activity coefficients to resolve this question?
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##### Re: How to obtain concentration of a FeG+ using activity coefficient?
« Reply #1 on: December 16, 2010, 07:03:30 AM »

Can use debye-hukal law to relate the concentration and ionic strength.
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#### Chaste

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##### Re: How to obtain concentration of a FeG+ using activity coefficient?
« Reply #2 on: December 16, 2010, 03:23:26 PM »

hi there, thanks for the contribution. The question has been there for a while and it has been solved.
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