Question #57ac0

1 Answer
Mar 28, 2017

Remember

#DeltaG = DeltaH - TDeltaS#

Thus #DeltarG = DeltarH - TDeltarS# because Change in a system is proportional to overall enthalpy, entropy or Gibbs free energy.

Thus for the reaction

#COCl_2 rarr CO + Cl_2#

We know everything except #DeltarS# so take it as x. Now write down the equation

#("-206 kJ")/"mol "= "-220kJ"/"mol" - 298.15K xx x#

Solve for #x#

#298.15 xx x = ("-220 kJ/mol") - ("-206 kJ/mol")#

#298.15 xx x = -14 #

#x = -14 /(298.15K)#

= # DeltarS = "-046.95623kJ"/"mol"#

As we are assuming that the #DeltarS# which we have found and #DeltarH# remains constant at 450K too we can now set up the equation

#DeltarG^@ = "-220kJ"/"mol" - (450K xx "-046.95623kJ/mol")#

#DeltarG^@ = "-220kJ"/"mol" - (450K xx "-046.95623kJ/mol")#

#DeltarG^@ = "-220 kJ"/"mol"-(-21.130.3035)#

#DeltarG^@ = "-220kJ"/"mol"+21.1303035#

#DeltarG^@ = "-198.8696965kJ"/"mol"#

Now we know that entropy or enthalpy cannot remain constant at different temerature so

#DeltarG^@ ~~ "-198.8696965kJ"/"mol"#