Hi anyoneee, why is the enthalpy change positive for a ligand exchange reaction that forms a less stable complex ion ? (pic with the specific qn will be uploaded in a bit ) thanks alot :)

Question

anonymous · Answer

http://oi65.tinypic.com/4lr477.jpg Option C is the right ans but I couldnt understand its explanation of why the enthalpy change is positive when it forms a less stable complex ion ><

kainui · Answer

So you have the reasoning for why $\Delta S >0$ so if we look here:

$$\Delta G = \Delta H - T \Delta S$$

Since $\Delta S$ is positive that means $-T \Delta S$ is negative so that must mean $\Delta H$ is positive! If it wasn't, this would be a spontaneous reaction since negative $\Delta G$ is spontaneous.

But that's _just_ math. Why should we think this? I think this makes intuitive sense since it requires heat, it's endothermic and we must put heat into the system to make the reaction go.

anonymous · Answer

Thank you kainui for ur detailed explanation !! ^^ medal awarded + bless u :)