Plz define HYDRATION ENTHALPY....?

it is the amount of heat evolved when 1 mole anhydrous or partially hydrated salt combines with required number of moles of water to form hydrate....

CaCl2(l) +6H2O(l)---}CaCl2.6H20

Define Hydration

It is the energy released when an ion of the element takes up water molecule and gets hydrated. In hydration enthalpy, energy is released.

The Standard Enthalpy of Hydration, DH°hyd, 298, is the heat evolved when 1 mole of gaseous ions become hydrated (surrounded by water molecules), measured under standard conditions.

Al3+(g) + aq ® Al3+(aq) DH°hyd, 298 = -4613 kJ mol-1

The higher the charge on the ions and the smaller their size, the more exothermic the hydration enthalpy.

When the solvent is other than water the process is referred to as solvation, with the term enthalpy of solvation, DH°solv, 298.

or visit to:- http://www.scribd.com/doc/38582471/Enthalpies-of-S...

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RE:

Plz define HYDRATION ENTHALPY....?

plz give d definition or provide a URL....

Is the amount of energy released when one mole of ions undergo hydration

hydration enthalpy(H.E) is the amount of energy released when 1 mole of gaseous cation is dissolved in water.

H.E is INVERSELY proportional to SIZE OF CATION.

Li+>Na+>K+>Rb+>Cs+;

thus on dissolving with water Li+ will release max amount of energy .