Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: JonGant on March 28, 2017, 09:42:08 AM
-
I am doing a chemistry project and need to approximate the quantifiable strength of ion-dipole interactions between water and both sodium and chloride ions. I am not sure how to calculate or find these values so any help would be appreciated. Thanks!
-
Welcome, JonGant!
Do you mean, the interaction between one single sodium or chloride ion and one single water molecule?
Then I'd just put partial charges on H and O, based on the known dipole moment of individual water molecules and their shape and size. Then, choose a reasonable position for the chloride or sodium ion, supposed to carry one electric charge. And finally, compute the sum of the electrostatic interaction energies.
Or is there anything more subtle in it?
"Ion-dipole" must exclude all rearrangements of the electrons I guess.
A better estimate would put many water molecules around each ion (essentially as many as fit without repelling an other), compute the electrostatic energy, and divide by the number of water molecules, but that's already complicated for an assignment.
I hope more people will jump in.