Exam 3 Flashcards
Ka =
(concentration products) / (concentration reactants)
pKa =
- log (Ka)
Ka =
10 ^ -(pKa)
if there is a buffer, you use…
HH: pH = pKa + log (B-/HB)
a diprotic acid will have __ equivalence points, midpoints, and buffer regions
2
a triprotic acid will have __ equivalence points, midpoints, and buffer regions
3
How does pH relate to pKa at any point in the buffer regime of titration curve?
HH equation: pH = pKa + Log(B-/HB)
when “removing” multiple H+ protons, which is the hardest to remove?
- first H+
- Ka1 > Ka2 > Ka3
steps for solving a polyprotic acid titration:
- equation (NIE)
- calculate mm.mol
- ICE table
- buffer? –> HH equation
- NO? –> pKa2/Ka2 –> ICE table –> HH
solubility product (Ksp) steps to solve:
- eon
- Ksp = (products)/(reactants) (aq)
- ICE table
- Ksp =
- x = solubility = (M)
would precipitate form? (steps:)
- NIE (s –> aq + aq)
- Ksp = # = (products)/(reactants)
- new Ms (calculate Psp = products/reactants)
- p </= K or p > K
would precipitate form? p </= K
no, ions in solution
would precipitate form? p > K
precipitation reaction
If something is a bronzed Lowry CA or CB it is also always a ___-
complex lewis structure (LB / LA)
Lewis Acid/Base: LB (Lewis Base)
has a lone pair that is “loses”
Lewis Acid/Base: LA (Lewis Acid)
“gains” an H+
ALL anions (-) that attach to central metal ion =
Lewis Bases
ALL cations (+) that attach to central atom =
Lewis Acids
H2O is a…
lewis base
H3O+ is a…
lewis acid
ligand
species that bonds to central atom in lewis A/B
- contains 2+ lone pairs (compounds) OR
- anions (-) ions attached
Cl-, Br-, CN-, and OH- are examples of
ligands (anions -)
coordination number
of species (ligands) around/by central atom
the more lone pairs…
the more H+ “donating” capability
PH (at equivalence point) =
1/2 (pka1 + pka2)
ΔS order for solid, liquid, gas
ΔSgas > ΔSliquid > ΔSsolid
if there are more gas moles on the RHS (products) > LHS (reactants), then ΔS =
(+)
if there are more gas moles on the LHS (reactants) > RHS (products), then ΔS =
(-)
if ΔS > 0 (+), the reaction is moving towards
disorganization, spontaneity, diffusion
if ΔS < 0 (-), the reaction is moving towards
organization
Gibbs Energy equation:
ΔGrxn = ΔHrxn - T*ΔSrxn
if ΔG > 0 (+) , the reaction is
not spontaneous
if ΔG < 0 (-), the reaction is
spontaneous
if ΔG = 0, the reaction is
at equilibrium
HH equation(s):
pH = pKa + log [B-/HB]
OR
pH = pKa - Log [HB/B-]
not buffer WA/WB pH and pOH equation(s):
pH = 1/2 (pKa - log (Ma))
pOH = 1/2 (pKb - log (Mb))
pKa =
-log(Ka)
OR
-log(Ksp)
Ka (OR Ksp) =
10^ -(pKa)
if a compound is very (-), it has a __ pH
high pH
- the more (-) = the higher pH
if a compound is (+), it has a ___ pH
low pH
pH + pOH =
14
(@ T=25C) Kw =
10^-14 = [H3O+][OH-]
(CA/CB): pKa + pKb =
- @ T=25C
14
(WA/WB): x = [H3O+] =
sqrt[Ka*Ma]
- GJ eqn
WB : x = [OH-] =
sqrt[Kb*Mb]
- GJ eqn
central metal ions are generally ___ charge
2+
Ag charge
1+
H2O charge
0
nh3 charge
0
CO charge
0
the __ molecule is listed first
central metal ion
Zn charge
2+
the charge at the end of a compound applies to…
the ENTIRE compound
“total charge” of a compound must add up to equal…
0
- (charge cation) + (charge anion) = 0
- (charge central ion) + (charge rest of compound) = 0
ligands are classified by
the # of shared e- w/ central atom
monodentate
only bind at 1 site
- share 1 pair of e-
polydentate
ligands that are more than 1 pair of e-
- can bind to central atom at multiple points
bidentates bind at…
and their coordination number is…
2 sites
- # = 2
4 bidentates
oxalate (ox), ethylenediamine (en), acetylacetonate (acac), phenanthroline (phen)
oxalate (ox): formula, formal charge, coordination #
- formula: (C2O4)^(2-)
- charge: (2-)
- coordination #: (2)
ethylenediamine (en): formal charge and coordination #
- charge: (0)
- coordination #: (2)
acetylacetonate (acac): formal charge and coordination #
- charge: (1-)
- coordination #: (2)
phenanthroline (phen): formal charge and coordination #
- charge: (0)
- coordination #: (2)
chelating agent
polydentate ligands used to extract a metal from solution
- ex: hexadentate ligand in EDTA
naming: anion (-) ligands
suffix-“o”
- Cl- = chloro-
- OH- = hydroxo-
- CN- = cyano-
- CH3CO2- = acetato-
- SO4^2- = sulfato-
- CO3^2- = carbonato-
naming: molecular ligands
their name
EXCEPT:
- H2O = aqua-
- NH3 = ammin-
naming: # of same type of ligands =
prefix
- di (2), tri (3), tetra (4), penta (5), hexa (6)
naming: complex ligand prefix
bis, tris
naming: complex ligand prefix
bis, tris
naming: if there are different ligands…
name them in alphabetical order
naming: the oxidation number is represented by
roman numerals at the end
- charge of central metal ion
naming: complex ion = anion (-) …..
suffix = “-ate”
Fe(ox)3
trisoxalate ferrate IV
CuI4
tetriodo cuprate II
You titrate 30 mL of 0.1 M selenious acid, H2SeO3 (pKa1 = 2.6, pka2 = 8.3) w/ 0.1 M NaOH to the 1st MIDPOINT of the titration. What expression is the correct way to find the pH?
pH = pKa1
CN charge
1-
enthalpy change (ΔH) =
(products) - (reactants)
entropy change (ΔS) =
(products) - (reactants)
ΔH and ΔG become equal at what temp?
0 K
at equilibrium, ΔG =
0
at a phase transition, ΔG =
0
phase transitions
vaporization: liquid –> gas
fusion: solid –> liquid
Boiling: 100C (liquid —> gas)
Melting: (solid —> liquid)
if ΔG = 0, then ____ equation is true
ΔH = T*ΔS
ΔG =
ΔH - T*ΔS
ΔS increase,
randomness/diversity increases
2nd Law: ΔSuniverse >
> 0
- always
- always moving towards spontaneity
2nd Law: entropy of the universe
ΔSrxn - ΔH/T > 0
criteria for spontaneity:
ΔHrxn - T*ΔSrxn < 0
an increase in volume causes a ___ in ΔS
increase in ΔS
ΔS ___ w/ increasing mass
increases
ΔG and ΔS have what relationship?
inverse
- ΔS = (+), ΔG = (-)
at 1 atm Gibbs equation states:
ΔGrxn = ΔH - T*ΔS
at equilibrium Gibbs equation states:
K = e^(-ΔG/RT)
- K = equilibrium constant
- R = 8.314 J/Kmol = 0.008314 kj/Kmol
- T = temp (K)
low temperatures are…
endothermic (-) = not spontaneous
high temperatures are…
exothermic (+) = spontaneous
common ion effect
solution w/ 2 compounds (1 similar ion)
- NIE = compound (1) –> ion + ion
- similar ion [M] starts w/ M amount
- solve SICE table
- can ignore “x” for common ion in Ksp = (E(common ion) = M)
@ pKa1, there is ___ amount of CA/CB(1)
50/50
@ pKa2, there is ___ amount of CA/CB(2)
50/50
when calculating the “end” row of the “SICE” table, you follow ____ format
(initial) +/- (stoichiometry)(x)
to calculate a new M for ions in a solution…
[1] = (1st mL)(M)/(total mL)
CN-, CO, NO2-, en =
strong ligands
- largest energy:
- CN- > CO > NO2- > en
H2O, ox, F-, Cl-, Br-, I- =
weak ligands
- largest –> smallest energy:
- en > H2O > ox > F- > Cl- > Br- > I-
ΔG units
kJ / mol
“spontaneity switch temp” =
ΔG = 0
- T = ΔH/ΔS
if ΔH and ΔS are both (+), the reaction is…
- low temp = not spontaneous
- high temp = spontaneous
if ΔH = (-) and ΔS = (+), the reaction is…
always spontaneous
- ΔG = (-)
if ΔH = (+) and ΔS = (-), the reaction is…
never spontaneous
- ΔG = (+)
if ΔH and ΔS are both (-), the reaction is…
- low temp = spontaneous
- high temp = not spontaneous
if ΔH and ΔS have the same sign, Temperature =
T spontaneity = switchable
- T = ΔH/ΔS
- below T and above T; spontaneity switches
- if ΔH = (+), ΔG = (+)
if you combine a solid with H2O, it is likely a…
dissociation reaction
- solid –> aq + aq
if you combine 2 solids w/ a common ion….
NIE can ignore 2nd solid
- initial M for common ion in “SICE” table = M of 2nd solid
SCN- name
thiocyanate ion
change in enthalpy
ΔH
change in entropy
ΔS
ΔS units
J/ kmol = kJ/kmol
ΔG units
kJ (or J) / mol or just kJ (energy change)
ΔH units
kJ/mol
J –> kJ
J * 10^(-3)
ΔH and ΔG are equal at what temperature?
0 K
What is the significance of the superscript in symbol ΔG∅?
superscript means gaseous species are at 1 atm partial pressure and ions are at 1 M conc’n
phase transition: M(s) –> M (g)
- what can be said about the Gibb energies of the solid and gaseous forms of substance M?
- Name of phase transformation?)
- G(M(s)) = G (M(g)).
- sublimation
∆H = (+) and ∆S = (-)….
will NEVER be spontaneous
What is the difference between ΔGrxn and ΔSrxn?
- ΔSrxn = rxn increases disorder or not
- ΔGrxn = would rxn ever happen under the conditions specified
Give the 2nd Law of thermodynamics in terms of entropy change of the universe.
a reaction is spontaneous only if
ΔSuniv > 0
What is the relation between ΔGrxn and ΔSuniverse?
ΔGrxn ≡ -T(ΔSuniv)
when calculating Δ from a table of values….
P - R
- (-) carries through!! to all reactants
- ((#)P + (#)P) - (#)R - (#)R
Relation b/w ΔG∅ and standard voltage, E∅:
ΔG∅ = -nFE∅
- n = # of e- transferred (given)
- F = Faraday’s constant ~ 96.5 kJ/mol*V
- E∅ = voltage
entropy increases w/
increasing mass
pKa > 7 =
Base!!
diprotic titration: pKa1 occurs at what volume?
1/2 mL of acidic species (given mL)
diprotic titration: equivalence point 1 occurs at what volume?
mL of acidic species (given mL)
diprotic titration (same M): pka2 occurs at what volume?
given mL (*1.5)
diprotic titration (same M): equivalence point 2 occurs at what volume?
- given mL. (*2)
LA and LB are always…
reactants
in the reaction quotient Q, the [] can be replaced w/ given…
concentration (M) or partial pressure (atm)
when given ΔS, you MUST ALWAYS…
CONVERT TO KJ
magnesium phosphate
Mg3(PO4)2
to make a buffer…
you need: CA/CB or WA/SB or SA/WB
- pka ≈ pH
polyprotic titration: to find mL titrant at equivalence point (1, 2, 3)…
m1v1 (analyte) = m2v2 (titrant)
- v2 = equivalence point 1
- v2 * 2 = equivalence point 2
- v2 * 3 = equivalence point 3
polyprotic titration: to find mL at pKa (1, 2, 3)…
- pka1 = 1/2 (mL equivalence point 1)
- pka2 = 1/2 (mL equivalence point 2)
- pka3 = 1/2 (mL equivalence point 3)
