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comparing the complexes: trans[Ir(PH3)2(CO)(H2)] cis[Ir(PH3)2(CO)(H2)] trans[Ir(

ID: 855943 • Letter: C

Question

comparing the complexes:
trans[Ir(PH3)2(CO)(H2)]
cis[Ir(PH3)2(CO)(H2)]

trans[Ir(NH3)2(CO)(H2)]
cis[Ir(NH3)2(CO)(H2)]

trans[Rh(PH3)2(CO)(H2)]
cis[Rh(PH3)2(CO)(H2)]

In terms of the topic of enthalpy/entropy and free energy, why would one of them be spontaneous. My results indicated that the trans complexes are spontaneous, cis non spotaneous and the complexes with Rh instead is nonspontaneous for both, why is this?

And also what does the difference between enthalpy and free energy tell is about the chemical transformations taking place?
Thanks!

Explanation / Answer

Generally stability of trans complexes is more than cis complexes, this is due to their least polar nature and high symmetry. Thus, trans complexes are more favorable than cis complexes. But rhodium is inert, so it tends to remain as a metal than in complex form.

The difference between free energy change and enthalpy change gives product of temperature and entropy change. That is entropy change indirectly tells about the disorderness of the reaction. If the disorderness increases, entropy increases.