CHEM 113:Exam four
25 Cards in this Set
Front | Back |
---|---|
Soluble Ionic Compounds
|
All common compounds of Group 1A (Na, K)
All common nitrates, acetates and most perchlorates
All common chlorides, bromides and iodides (except Ag, Pb, Cu and Hg2) and all common fluorides (except Pb and Group 2A)
All common sulfates (except Ca, Sr, Ba, Ag, and Pb
|
Insoluble Ionic Compounds
|
All common metal hydroxides (except group 1A)
All common carbonates and phosphates (except group 1A and NH4)
All common sulfides are insoluble (except group 1A, Group 2A and NH4)
|
Solubility and Equilibrium
|
A saturated solution contains max amount of dissolved solute in the presence of undissolved solute
An unsaturated solution contains less than the equilibrium concentration of dissolved solute. If more solute is added, it will dissolve
|
Effect of pH on Solubility
|
The addition of H3O will increase the solubility of a salt that contains the anion of a weak acid
|
Predicting the Formation of a Precipitate
|
If Q > K, a precipitate will form
|
Selective Precipitation
|
A precipitation ion is added to the solution until the Q of the more soluble compound is almost equal to K
The less soluble compound will precipitate, leaving behind the ion of the more soluble compound
|
Complex ion formation
|
Complex ions form when a central metal cation becomes covalently bonded to two or more anions and/or molecules
|
Spontaneous change
|
One that occurs without a continuous input of energy
|
Freedom of Particle Motion
|
All spontaneous endothermic processes result in an increase in the freedom of motion of the particles in the system
|
Molecular interpretation of entropy
|
S = k lnW
S: entropy
W: microstates
K: Boltzmann constant
|
Entropy
|
A system with fewer microstates has lower entropy
A system with more microstates has higher entropy
All spontaneous endothermic processes exhibit an increase in entropy
|
Concept of delta S
|
deltaS = qrev/T
|
Second Law of Thermodynamics
|
All real processes occur spontaneously in the direction that increases the entropy of the universe
For a process to be spontaneous, a decrease in the entropy of the system must be offset by a larger increase in the entropy of the surroundings
|
Standard Molar Entropies
|
S0 is the standard molar entropy of a substance, measured for a substance in its standard state in J/molK
1 atm for gas, 1M for solutions, substance in its most stable form for solids and liquids
|
Factors affecting entropy
|
Temperature (temp increases, S0 increases)
Physical state (disorder increases, S0 increases)
Formation of a solution
Atomic size and molecular complexity (atom size increases, S0 increases)
|
Entropy change and dissolution of a salt
|
The entropy of a salt solution is usually greater than that of the solid and of water
|
Entropy of gas dissolved in liquid
|
Entropy of a gas is already so high that it decreases when the gas dissolves
|
Standard entropy of reaction
|
ΔSºrxn is the entropy change that occurs when all reactants and products are in their standard states
|
Predicting the Sign of ΔSºrxn
|
ΔSºrxn is positive if the amount of gas increases
ΔSºrxn is negative if the amount of gas decreases
ΔSºrxn is likely to be positive if a new structure forms that has more freedom of motion
|
Entropy changes in the surroundings
|
A decrease in the entropy of the system is outweighed by an increase in the entropy of the surroundings
In an exothermic process, the surroundings absorbs the heat released by the system and Ssurr increases
In an endothermic process, Ssurr decreases
|
Temperature at which heat is transferred
|
The heat transferred is specific for the reaction and is the same regardless of temperature
The impact on the surroundings is larger when they are at lower temperature because there is a greater relative change in Ssurr
|
ΔSºuniv for spontaneous reactions
|
Exothermic reactions will always be spontaneous
For endothermic reactions where ΔSºsys < 0, ΔSºsurr must be larger thanΔSºsys for the reaction to be spontaneous
For endothermic reactions where ΔSºsys > 0, ΔSºsurr must be smaller than ΔSºsys for the reaction to be spontaneous
|
Gibbs Free Energy
|
ΔG is a measure of the spontaneity of a process and of the useful energy available from it
ΔG < 0 for spontaneous
ΔG > 0 for nonspontaneous
ΔG = 0 for equilibrium
|
Calculating ΔG
|
ΔGsys = ΔHsys - TΔSsys
ΔGºrxn = ΣmΔGproducts - ΣnΔGreactants
|
ΔG and Useful Work
|
ΔG is the max useful work done by a system during a spontaneous process
ΔG is the minimum work that must be done to a system to make a nonspontaneous process occur
|