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hydration of ions

hey peeps, i havent made a thread on here for quite a wile now. Can ne1 explain to me why heat is released upon hydration of ions once they are formed (having just been ionised). :confused: :smile:
Reply 1
Avatar for vinny2256
vinny2256
6
because it's an exothermic occurence.
Reply 2
Avatar for ryan750
ryan750
OP
2
vinny2256
because it's an exothermic occurence.


oh yeah - good point. thanks mate
Reply 3
Avatar for Ralfskini
Ralfskini
10
vinny2256
because it's an exothermic occurence.



This is possibly the worst answer you can give.
Reply 4
Avatar for vinny2256
vinny2256
6
Ralfskini
This is possibly the worst answer you can give.


lol fine them smart ass.

When water molecules form polar bonds with the ion, much energy is given out as the polar bonds are of a lower energy level than the ionic bonds thus this energy is dissipated as heat to the surrounding solution. The higher the charge density of the ion in solution, the easier it is for it to gain/lose electrons. The overall process involves the ions being attracted to the water molecules thus more energy OUT than what is taken IN.
vinny2256
lol fine them smart ass.

When water molecules form polar bonds with the ion, much energy is given out as the polar bonds are of a lower energy level than the ionic bonds thus this energy is dissipated as heat to the surrounding solution. The higher the charge density of the ion in solution, the easier it is for it to gain/lose electrons. The overall process involves the ions being attracted to the water molecules thus more energy OUT than what is taken IN.


Just one problem, what are polar bonds? I think you might be talking about the ion-dipole interaction of the hydration shell. Still a poor answer.

look here:

http://www.science.uwaterloo.ca/~cchieh/cact/applychem/hydration.html
Reply 6
Avatar for john !!
john !!
14
make bonds = lose potential energy = gain kinetic energy = raise temperature of mixture = lose heat to surroundings = exothermic
that would be my guess....
The energy of hydration is always negative because of the strong ion-solvent interactions, i.e. the ions are more energetically stable when solvated.

However, this does not equate to heat energy being released on solvation of an ionic solid. One has to set up a Born-Haber cycle with the lattice energy and the energy of hydration in order to work out the energy of solvation (which can be either negative or positive).

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