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How is equilibrium constant of a reaction related to the temperature of reaction?

How is equilibrium constant of a reaction related to the temperature of

reaction?

Grade:12th pass

1 Answers

Akshay Meena
askIITians Faculty 34 Points
10 years ago

Although, The exact calculation of the effect of temperature changes upon an equilibrium is somewhat more involved than we can treat here, we can make several approximate relationships that are very useful. Remember that the equilibrium constant is related to the standard free energy change of the reaction

                                                                

And recall that the free energy change upon reaction is related to both the enthalpy and entropy changes

                                                          

Although the free energy change is strongly dependent on temperature, usually the enthalpy and entropy changes upon reaction are NOT temperature dependent (or at least not very much so). This implies that the free energy is a linear function of temperature. Combining the above two equations:

                                                            

substituting in the equilibrium constant

                                                      

and finally

                                                

Remember that the enthalpy and entropy changes are regarded as constants with respect to temperature, so the equilibrium constant is exponentially dependent on temperature. The relative change in equilibrium constant as a function of temperature is usually not expressed as above but as the van''t Hoff equation

                             

 

Thanks & Regards
Akshay Meena, 
askIITians Faculty
M.Tech, IIT Kharagpur

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