[AngelShare]

I'm supposed to use this site to answer 10 questions. I've answered all but one and I can't figure it out for the life of me.

Describe the process when a polar solvent dissolves an ionic substance.

I'm only supposed to use the first eight slides...but I still don't understand. If someone would be kind enough to look over the slides and tell me which one the answer can be found on if I'm overlooking an obvious answer I'd appreciate it. I've looked over the first eight slides about seven times and I've checked all over the internet but I still can't get it.

Oh and, here is one question I answered...

Why would SO2 go down in solubility when temperature increases?

SO2 goes down in solubility as temperature increases because it's a gas and solubility always decreases for gases.

...Could someone explain to me why that is? I know the answer but I'm not sure I understand it and that won't do me much good.

[Yggdrasil]

Re the SO₂ question:

For many reversible processes (e.g. the dissolution of a solute), there is usually a competition between enthalpy (potential energy) and entropy (randomness or disorder).  Recall that (delta)G = (delta)H - T (delta)S.  In general, reactions will proceed in the dirrection of lowering potential energy and increasing the entropy of the system.  Since the dS (change in entropy) term is modified by the temperature term, at high temperatures, the reaction would rather increase entropy than decrease its potential energy.  Conversely, at low temperatures, the system seeks a state of low energy over a state of low order.

So, in the case of the disolution of a gas, entropy decreases because a gas is more "random" or disordered than an aqueous solution.  Gas molecules in the gas phase are free to move about randomly whereas they are restricted by interactions with the solvent in the aqueous phase.  However, the solutes are at a lower energy when disolved than when in the gas state.  In the gas phase, there are no stabilizing interactions between molecules whereas interactions between the solvent and solute molecules stabilizes the solutes and puts them in a lower energy state.

Therefore, at low temperature, the gas molecules prefer the low energy (aqueous) state, whereas at high temperature, the gas molecules prefer the low order (gaseous) state.

The same logic applies to the disolution of solids.  Aqueous solids are less ordered by higher energy than a crystaline solid.  Therefore at low temperature, the molecules prefer the solid state (low energy), whereas at high temperature, they prefer the aqueous state (low order).