Chem Notes Exam 3

Chem Notes Exam 3 - Chem 102 Notes Exam 3 Solubility...

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Chem 102 Notes Exam 3 Solubility Products Consider the equilibrium that exists in a saturated solution of BaSO 4 in water BaSO 4(s) Ba 2+ (aq) +SO 4 2- (aq) Equilibrium expression: K sp =[Ba 2+ ][SO 4 2- ] where the equilibrium constant , K sp , is called the solubility constant K sp is not the same as solubility Solubility is generally expressed as the mass of solute dissolved in 1 L (g/L) or 100 mL (g/mL) of solution, or in mol/L (M) Factors Affecting Solubility The Common-Ion Effect o If one of the ions in a solution equilibrium is already dissolved in the solution, the equilibrium will shift to the left and the solubility of the salt will decrease BaSO 4(s) Ba 2+ (aq) +SO 4 2- (aq pH o If a substance has a basic anion, it will be more soluble in an acidic solution o Substances with acidic cations are more soluble in basic solutions Complex ions o Metal ions can act as Lewis acids and form complex ions with Lewis bases in the solvent o The formation of these complex ions increases the solubility of the salts Amphoterism o Amphoteric metal oxides and hydroxides are soluble in strong acid or base, because they can act either as acids or bases o Examples of such cations are Al 3+ , Zn 2+ , Sn 2+ Will a precipitate form? In a solution o If Q=K sp , the system is at equilibrium and the solution is saturated
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o If Q> K sp , more solid with dissolve until they are equal o If Q<K sp , the salt will precipitate until they are equal Selective Precipitation Ions One can use differences in solubility’s of salts to separate ions in a mixture First Law of Thermodynamics Recall that energy cannot be created nor destroyed Therefore, the total energy of the universe is a constant Energy can, however, be converted from one form to another or transferred from a system to the surroundings or vice versa Spontaneous Processes Spontaneous processes are those that can proceed without any outside intervention Processes that are spontaneous in one directions are non-spontaneous in the reverse direction Processes that are spontaneous at one temperature may not be spontaneous at other temperatures Reversible Process In a reversible process, the system changes in such a way that the system and surroundings can be put back in their original states by exactly reversing the process Irreversible Processes Irreversible processes cannot be undone by exactly reversing the change to the system Spontaneous processes are irreversible (without outside intervention) Ent ropy Ent ropy (S) is a term coined by Rudolph Clausius in the 19 th century Clausius was convinced of the significance of the ratio of heat delivered and the temperature at which it is delivered q_ E=q+w Δ T Entropy can be thought of as a measure of the randomness of a system
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H is related to the various modes of motion in molecules Like total energy, E, and enthalpy, H, entropy is a socalled state function (pg. 254)
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This note was uploaded on 04/17/2008 for the course CHEM 102 taught by Professor Williamson during the Spring '08 term at Texas A&M.

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Chem Notes Exam 3 - Chem 102 Notes Exam 3 Solubility...

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