Feb 19th SI

SI Chem 178
Ch 16 (Acid/Base Equilibrium)
Feb 19, 2013
Leader: Emily
Suggested probs for Fri: 76, 83, 86, 90, 97, 100, 114
A good prob for review: 16.62
What is true of the concentrations of a dissociated
monoprotic acid’s proton and conjugate base? How
does this help with/relate to calculations? How
does this change with di/polyprotic acids?
16.59 b/c only - You
more practice if you
b. What is the pH of
chromate ion? (HCrO4
Deg C.
can do “a” on your own for
like : )
a solution of 0.100M hydrogen
-2) with a Ka of 3*10^-7 @25
c. What is the pH of a 0.120M solution of pyridine?
(a base with the chemical formula C5H5N, and a Kb
of 1.7*10^-9)
New Concepts:
Dilution of reactants- Our old buddy Le Chatelier
returns! … in an HX  H+ + A- equilibrium
reaction, which direction will the reaction go if
Dilute the solution? (What happens in this case
Concentrate the solution? (What happens to my %
ionization here?)
What previous Concept of Le Chatelier is this
similar to?
Ka x OR + Kb = Kw = _______ (For a acid conjugate
pKa + OR x pKb = pKw = _______
Deg C)
(at 25
What does that “p” stand for? ___________
A smaller pKa means a stronger/weaker acid? How
can we reason through this if we didn’t know the
If Ka for benzoic acid is 6.3*10^-5, what is its
Kb? Is there more than one equation we can use for
What are the three things we have discussed that
affect acid strength? Describe their directional
relationships on the PT.
Strength comparisons…..
HI >/< HF . . . Why?
HClO2 >/< HClO4 . . . Why?
CH4 >/< than H2O . . . Why?
H2SO4 </> than H2CO3 . . . Why?
H2CO3 >/< than H2NO3 . . . Why?