Test 3 + some final stuff - Chem 112- Summer Flashcards
Ksp
solubility equilibrium/solubility product constant, for ionic compounts treated as insoluble typically. Since it is a salt –><– cation + anion, the salt is a solid and is not included in the equilibra
molar solubility
moles/L of a saturated solution (so its the x in an ICE table or the E)
solubility
number of grams of solute in 1L of saturated solution
when Q < Ksp
no precipitate
when Q > Ksp
precipitate
Q= Ksp
no precipitate
factors that affect solubility
common ion effect, pH, formation of complex ions
common ion effect
suppresses the ionization of an electrolyte when another electrolyte (that contains a common ion) is added
how does pH affect solubility
solubility increases as the pH decreases (i.e. if you add an acid, the solubility will increase and move forward)
thermodynamics
the science dealing with heat and the relationship with other forms of energy. thermodynamics can predit whether a process will occur (but it does NOT predict amount of time required for process)
spontaneous process
occurs without outside intervention under specific set of conditions
nonspontaneous
does not occur without outside intervention (CONTINUAL input of external energy)
first law of thermodynamics
any change in internal energy is due to either heat or work (this energy can be kinetic or potential)
change in U
change in U = q + w
U is change in internal energy. q is heat. w is work.
thermochemistry
the study of the heat absorbed or released during chemical and physical changes
what is work
force applied x distance traveled. work involves movement
enthalpy letter
H,, change in H
enthapy def
a thermodynamic quantity.
change in H= change in U + P(change in V)
but it is also change in H = q (aka heat)
exothermic processes tend to be what
spontaneous. BUT this is not guarenteed
Entropy letter
S,, change in S
entropy def
entropy is a state function. it is a thermodymanic quantity that measures the amount of disorder in a system. to predict spontainiety, both enthapy and entropy must be known.
boltzman’s def
measure of disorder. S=KlnW
as temp increases ENTROPY of a system does what
decreases
S of different states
S gas > S liquid > S solid
more microstates = what
higher entropy
K = what
boltzmann’s constant (1.38 x 10^-23 J/K)
W= what
microstates (number of diff arrangements)
probabulity distributiion of microstates
W=X^N
X= number of cells in a volume
N = number of molecules
change in entropy
change in S system= S final- S initial
standard entropy
absolute entropy at 1 atm
choose one:
S increases with (larger/ smaller) molar mass
larger. entropy increases with larger molar mass
S increases with (more/ less) molar complexity
more molar complexity
change in S universe
= change in S system + change in S surroundings
change in S universe > 0
spontaneous
change in S universe < 0
nonspontaneous (spontaneous in reverse reaction)
change in S universe = 0
equilibrium
Second law of thermodynamics
change in S universe stuff
third law of thermodymanics
entropy of a pure perfect crystal substance at 0K is equal to 0. at 0, molecular movement stops. only one way to arrange the molecules at this point. Cannot go lower than 0K
change in S (in relation to other S)
change in S= S products- S reactants
gibbs free energy (def and equation)
measure of available energy. change in entropy is directly porportional to enthaply of a system
change in S surrounding = (-change in H system)/T
gibbs free energy more direct equation
change in G = change in H - T (change in S)
change in G < 0
spontaneous in forward
change in G > 0
non spontaneous in forward
change in G = 0
equilibrium
what is G
gibbs free energy (spontaniety)
spontaneous reactions generally have what
change in H < 0
change in S > 0
change in G < 0
for a reaction to be spontaneous in low temp
change in G > 0 for an endothermic raction
or
change in G < 0 for an exothermic reaction
exothermic reaction means what for change in H
change in H > 0
exothermic reaction means what for change in H
change in H < 0
for a reaction to be spontaneous in high temp
change in G < 0 for endothermic and exothermic
for a reaction to be nonspontaneous in high temp
change in G > 0 for endothermic and exothermic
for a reaction to be nonspontaneous in low temp
change in G> 0 for endothermic
or
change in G< for exothermic
to find temp at which spontaneity changes when G=0
T= change in H/change in S
standard free energy symbol and def
symbol = change in G degrees
def= free energy change for a reaction when it occurs under standard state conditions
when K >1, change in G degrees is what
when K >1= -( change in G degrees)
when K < 1, change in G degrees is what
when K >1= + ( change in G degrees)
when Q < K, change in G degrees is what
negative
when Q > K, change in G degrees is what
positive
addative free energy change
change in G 3= change in G 1 + change in G2
oxidation
loss of electrons
reduction
gaining electrons
reducing reaction
loss electrons
oxidizing agent
gain electrons
hydrogen has what oxidation number
+1
oxygen has what oxidation number
-2
balancing redox reaction steps (acidic)
- write half reactions
- balance half reactions
- balance O by adding H2O
- balance H by adding H+
- balance charge by adding electrons
- make electrons =
- add half reactions together
balancing redox reactions (basic)
normal steps +
1. for H+ ions, add on OH- to BOTH sides
2. make additional cancellations of all ner H20 molecules
what are galvanic (voltaic) cells
cells that use spontaneous redox reactions to produce electrical energy
anode
negatively changed metal electrode responsible for oxidation (the oxidation side of reaction)
cathode
positive changed metal electrode responsible for reduction (the reduction side of reaction)
why does current flow and what direction (anode vs cathode)
flows from anode to cathode. does this because there is a difference in electrical potential energy
Ecell
electrical potential/cell potential. measured by voltmeter
cell notation
left side is anode, right is cathode
E degrees=
E cathode - E anode (you will need to look these values up)
E degrees > 0
spontaneous
E degrees < 0
nonspontaneous
redox is spontaneous if (3 things)
- E degree cell is positive
- change in G degree is negative
- K is greater than 1
if E degree is negative, it means what
non spontaneous, so charge is flowing from cathod to anode (reverse direction)
when Q>1, E (< / >) E degrees
Q >1, E < E degrees
when Q< 1, E (< / >) E degrees
Q< 1, E > E degrees
when given numbers, which is the anode and which is cathode
the smaller one is anode, the larger is cathode
for standard cell potential (the change in E degrees) equation, do you need to pay attention to stoichiometry?
no. so DON’T multiply to make them equal.
