Question

Hydration energy. The hydration enthalpy (ΔH_hyd.)is defined as the heat released upon placing gas-phase ions into water, forming the hydrated ions:

Mⁿ⁺(g) Mⁿ⁺(aq)

Using the references supplied, calculate the hydration enthalpies of all of the divalent cations (M²⁺) for the 1^st-row transition metals. Plot ΔH_hyd. vs. identities of 1^st-row transition metals. Use crystal field theory to explain why these energies do not monatonically increase across the series of elements.

Dont need references to calculate

Answer 1

calculation of CFSE

for each electron in t₂g orbital, energy decreases by 0.4o and for each electron in e_g orbital energy increases by 0.6o.

for example NI ²⁺ , it is d⁸ system,

configuration :  t₂g (6)  e_g(2)

CFSE = -0.4_o6 + 0.6_o2 = -1.2 _o

CFSE gives stabilisation energy to hydration enthalpy in all the configurations except d5 and d10 due to zero CFSE.

hydration enthalpy is guided by the stability of the formation of aqua-complex with metals which thereby depends on the CFSE.