Titration Flashcards
F
Formal concentration:
about moles of “original chemical formula” in solution per liter
Note: Refer to F OF TITRANT!
(F will increase in any case, since titrant is keep being added)
Ve
Equivalence point:
the point where stoichiometric amount of titrant and analyte reacted
Conjugate base pair of analyte react with water to increase p().
Ex) WA,SB titrant: conjugate base of weak acid (weak base) react with water, inc. pH as it forms OH-.
See paint.
M
Molar concentration:
about moles of “each chemical species” in solution per liter
(1/2)Ve
Half of equivalence point:
the point where half of titrant was added to form the next compound.
the pt where half of titrant got deprotonated (if titrant was acid)
[HA]=[A-] if titrant was acid
[HB]=[B-] if titrant was base
Le Chatlier’s principle
Predict effect of change in chemical rxn in species
adding more reactant -> more product
Common ion effect
If there are ions of the same kind already dissolved in solution, then solubility of the ion is lower
than if there are no ions of same kind present in sol’n.
K
Equilibrium constant
K=( [C]^c [D]^d / [A]^a [B]^b )
Ka
Acid dissociation constant
HA-> H+ A-
Ka=( [H+][A-] ) /[HA]
∴ Bigger Ka means the acid dissociated to give out H+ more, and therefore indicates stronger acid
pH
-log[H+]
14-pOH
pKa
pKa=-log[Ka]
Note: just like smaller pH indicates stronger acid, smaller Ka indicates stronger acid.
Henderson-Hasselbalch equation
ONLY WORK FOR WEAK ACID OR BASE
pH=pKa+log([A-]/[HA])
pOH=pKb+log([BH+]/[B-])
Henderson-Hasselbalch equation at (1/2)Ve
pH=pKa if titrant was acid
pOH=pKb if titrant was base
∵log1=0
and the solution is either weak acid or base at (1/2)Ve
Mass balance
Formal concentration = all form of the species
Before Ve
[analyte] determines pH
After Ve
[titrant] determines pH
pF,pKa,pH
pH and pKa are smaller for stronger acid.
pF is small if much titrant is added (don’t relate to acidity)
UNLESS compare to pKa
pF>7
AT Vi or Ve
pH=7
Since Not much F were added to solution, no pH change.
Q-what if starting pH was SA/SB, and not neutral water? Would I then need to calculate pH of starting species
pKb given
DON’T do: 14-pKb to get pKa IF solution is base
DO: 14-pkb to get pKa IF solution is acid
pKa less than pF
at Vi or Ve
Ka>F
strong-acid-like-behavior
(HA dissociates to give out H+ more)
pH=pF
m=1 (ignoring sign)
pKa>pF
AT Vi or Ve
Ka is smaller than pF
pH is half of sum of pF and pKa, m=1/2(WA like)
