Consider the cis doubleheadarrow trans isomerization reaction at 300K: (cis) C_2
ID: 530311 • Letter: C
Question
Consider the cis doubleheadarrow trans isomerization reaction at 300K: (cis) C_2H_2D_2 doubleheadarrow (trans) C_2H_2D_2 a. One mole of the (cis) gas is introduced into a chamber and allowed to isomerize, forming the (trans) isomer. At equilibrium, there is an equimolar mixture of the two forms. Determine Delta G when the extent of the reaction is 0.1 (i.e. when the amount of trans formed is 0.1 moles). b. What is Delta G for a mixture of 0.9 moles of trans and 0.1 moles of cis? What is the difference between this result and that of part a) and what does it mean?Explanation / Answer
a) Cis isomer <-----> trans isomer
at equilibrium 1-X X
given X = 0.1 , hence cis = 1-0.1 = 0.9 , trans = 0.1
K = [Trans] /[Cis] = ( 0.1/0.9) = 0.111
dGo = -RT ln K
= -8.314 x 300 x ln ( 0.111)
= 5480 J/mol
b) K = [Trans] /[cis] = 0.9/0.1 = 9
dGo = - 8.314 x 300 ln 9
= - 5480 J/mol
when dGo is negative the reaction or process is spontanoues
Hence when trans isomer is more than cis we get dGo negative.
This indicates cis conversion to trans is spontanoues process
This indicates trans isomer is more stable than cis isomer