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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: taylor on April 04, 2009, 05:44:26 AM

Title: thermo question-dont believe enough info given
Post by: taylor on April 04, 2009, 05:44:26 AM

hey guys ive got a question ive never seen before. 
"carbon dioxide is produced in the combustion of carbon in the presence of oxygen. calculate the value of S⁰ for the oxidation of carbon as graphite to carbon dioxide: C _{(s, graphite)}+0₂ >CO₂
thanks for any help

Title: Re: thermo question-dont believe enough info given
Post by: lancenti on April 04, 2009, 05:47:19 AM

S = q/T = -dH/T

q: Heat absorbed by the surroundings
T: Temperature of the surroundings
S: Entropy Change

So you'll need dH_combustion and using that you can work out the dS for the reaction.

Title: Re: thermo question-dont believe enough info given
Post by: taylor on April 04, 2009, 07:23:52 AM

thanks for the reply but how do i work out dH? isnt there too many variables?

Title: Re: thermo question-dont believe enough info given
Post by: lancenti on April 07, 2009, 11:33:49 AM

dH is basically the enthalpy change of the reaction. You can work this out using Bond Energies, since the energy released has to be the difference in bond energies (by Conservation of Energy)