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Inorganic Chemistry |
Hydration of Ions |
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(i) Hydration represents for the dissolution of a substance in water to get adsorb water molecule by weak valency force. Hydration of ions is the exothermic process (i.e energy is released during hydration) when ions on dissolution water get hydration.
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(ii) The energy released when 1 mole of an ion in the gaseous state is dissolved in water to get it hydrated is called hydration energy M(g)+ + Aq —> M+(eq); ΔH = –ve.
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| (iii) Smaller the cation, greater is the degree of hydration. Hydration energy is in the order of, Li+ > Na+ > K+ > Rb+ > Cs+ |
| (iv) Li+ being smallest in size has maximum degree of hydration and that is why lithium salts are mostly hydrated, LiCl. 2H2O also lithium ion being heavily hydrated, moves very slowly under the influence of electric field and, therefore, is the poorest conductor current among alkali metals ions It may, therefore, be concluded that it is the degree of hydration as well as the size of ion is responsible for the current carried by an ion. |
| Relative ionic radii Cs+ > Rb+ > K+ > Na+ > Li+ |
Relative hydrated ionic radii Li+ > Na+ > K+ > Rb+ > Cs+ |
Relative conducting power Cs+ > Rb+ > K+ > Na + > Li+ |
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