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### AuthorTopic: The standard-state free energy-thermodyanmics homework problem?  (Read 2352 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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#### brasarehot

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##### The standard-state free energy-thermodyanmics homework problem?
« on: January 20, 2012, 06:23:10 PM »

The standard-state free energy of hydrolysis of acetyl phosphate is - 42.3 kJ/mol. a) Calculate the free energy for acetyl phosphate hydrolysis in a solution containing 2 mM acetate, 2 mM phosphate , and 3 nM acetyl phosphate. b) What ratio of concentrations of reactants to that of the products will make the reverse reaction (formation of acetyl phosphate from phosphate and acetate ion) energetically favorable?

My attempt...please tell me if my thinking is correct
a) deltaG = -42300 + 8.314(298)ln[(2x10^-3)(2x10^-3)/(3x10^-9)]
b) 42300 = 8.314(298)ln(?), ? = 25988554.67
so... reactants:products < 25988554.67
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#### UG

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##### Re: The standard-state free energy-thermodyanmics homework problem?
« Reply #1 on: January 21, 2012, 11:26:36 AM »

a) deltaG = -42300 + 8.314(298)ln[(2x10^-3)(2x10^-3)/(3x10^-9)]
The working looks alright.
For question b, I think what they mean by energetically favourable is that the reaction becomes spontaneous. Do you know what value the Gibbs free energy change must be for the reverse reaction to be spontaneous? Once you work this out, substitute this into the equation you had for a) to find Q, the reaction quotient and then you can find the ratio of products : reactants.
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