Terms Contributing to Activation Parameters

Interchange expect a small change in entropy, i.e. AS is close to zero. Remember to distinguish between the mechanism and the individual steps in it. 

Ion-molecule expect a small increase in entropy. A S is slightly +ve. 

Molecule-molecule with a charge-separated activated complex expect a decrease. A S is slightly — ve. 

Molecule-molecule without charge separation in the activated complex expect a small increase or decrease. A 5 is slightly +ve or — ve. 

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