Hydration Enthalpy: Key Concepts
The enthalpy of hydration measures the energy released when gaseous ions interact with water molecules. A higher (more negative) value indicates stronger interactions.
Hydration Factors for Complexes
For octahedral complexes like these, with a constant charge (+2), the hydration enthalpy depends mainly on the ionic radius of the central metal ion. Smaller ions have higher charge density, leading to stronger hydration.
Comparing Metal Ion Radii
Let's examine the ionic radii (in picometers, pm) for the relevant +2 ions:
- Ca2+: ~100 pm
- V2+: ~78 pm
- Cr2+: ~84 pm
- Mn2+: ~83 pm
The order of ionic radii is: V2+ < Mn2+ < Cr2+ < Ca2+.
Identifying the Highest Hydration Enthalpy
The metal ion with the smallest radius, V2+, possesses the highest charge density.
Therefore, $[V(H_2O)_6]^{2+}$, featuring V2+, exhibits the strongest ion-dipole interactions with water and thus has the highest enthalpy of hydration among the given options.
Important Questions from Coordination Chemistry
An aqueous solution of $Co(ClO_4)_2 \cdot 6H_2O$ is light pink in colour. Addition of conc. HCl results in an intense blue coloured solution due to the formation of a new species. The new species among the following is
[Given: Atomic number of Co = 27]- Among the following, the compound with the lowest CO stretching frequency is
The rates of substitution for the following reaction vary with L in the order
- Identify X in the reaction, $[Pt(NH_3)_4]^{2+} + 2 HCl \rightarrow X$
Among the given platinum(II) complexes, the one that is thermally the most unstable is
