Solutions and their Properties

The properties of solutions are dominated by the intermolecular forces between solute and solvent. Remember what these looked like?

The solute-solvent forces make new structures (order) in the solution

But the solute breaks up the structure (order) that the liquid solvent may already have.

Some dissolution processes are quite complex and depend on different sides of a molecule doing different things. Such is the case with the action of SOAP (detergent) on a grease stain.

Solids and Gases make solutions. One possible method of storing hydrogen gas (for fuel) is by taking advantage of its' solubility in noble metals...

Solid-Solid solutions particularly of metals are sometimes called ALLOYS

We understand much of the dissolution phenmomenon through its energetics (thermodynamics)

The energetics of the dissolution of Ionic Salts to for Electrolytes is particularly interesting because the LATTICE energy and HYDRATION energies are both very high, but sometimes almost exactly cancel out.

Solutions can be UNSATURATED, SATURATED, or SUPERSATURATED...

A saturated solution has the same rate precipitation and dissolution.

Saturated concentrations (solubilities) depend strongly on temperature.

Gases dissolve in liquids like solids, but usually have much simpler behavior. For example, gases are less soluble at high temperature than at low temperature.

The constuency of mixtures is expressed by various concentration units. Know the definitions of each of the following useful measures of concentration

The solubility of a gas depends on its partial pressure above the solution.

Henry's Law

The vapor pressure of a solvent depends on how pure it is.

Raoult' Law

Impurities in a substance cause a change in its phase diagram by making the liquid region bigger.

The addition of solute RAISES the boiling point of a solvent

The addition of solute LOWERS the freezing point of a solvent

OSMOSIS is the movement of solvent through a membrane to equalize the concentration on both sides.

The pressure required to allow for no transport of solvent across the membrane is called the OSMOTIC pressure and obeys the relation:

Osmotic pressure has a great effect on living CELLS, because their walls are a semipermeable membrane.

(a) crenation is caused by water movement out of a cell in a hypertonic solution.

(b) hemolysis is caused by water movement into a cell in a hypotonic solution.

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