CHEM 101DL Study Guide - Midterm Guide: Benzylamine, Init, Weak Base
26 Jun 2018
School
Department
Course
Professor
Chemistry 101DL Summer Session I, 2018
Duke University Dr. T. Woerner
Problems (Acid, Base, pH) - Solutions
1. A 0.200 M solution of dichloroacetic acid, , a weak monoprotic
acid, is 33% ionized. What is the ionization constant of this acid?
Let's abbreviate the acid as HA:
HA(aq) +
33% ionized means that at equilibrium . We already know that since
the % ionization is so high it is not a good idea to place initial conditions into the
equilibrium expression. Thus, as we know it is 33% ionized at equilibrium, the
equilibrium [ ] = 33% of 0.2 or 0.066. So,
2. A solution is prepared by dissolving 0.300 moles of cyanoacetic acid,
, in sufficient water to make exactly one liter of solution. The
concentration of in the resulting solution is 0.032 M. What is the ionization
constant of cyanoacetic acid?
Again, let's abbreviate the weak acid as HA. Thus,
HA(aq) +
initial 0.30 0 0
equil. 0.3 – 0.032 0.032 0.032
C C
Cl
H
Cl
O
O H
H+
(aq)
A–
(aq)
!
"
#
#[H+
(aq)]
[HA(aq)] $
%
&
&100 = 33
H+
(aq)
K =
[H+
(aq)][A–
(Aq)]
[HA(Aq )] =
[H+
(aq)]2
[HA(aq)] = (0.066)2
(0.2−0.066) = 3.2X 10–2
C C
CN
H
H
O
O H
H+
(aq)
H+
(aq)
A–
(aq)
K =
[H+
(aq)][A–
(Aq)]
[HA(Aq )] =
[H+
(aq)]2
[HA(aq)] = (0.032)2
(0.3 – 0.032) = 3.82X10–3
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Document Summary
O: a 0. 200 m solution of dichloroacetic acid, We already know that since the % ionization is so high it is not a good idea to place initial conditions into the equilibrium expression. Thus, as we know it is 33% ionized at equilibrium, the equilibrium [ = 3. 2x10 2: a solution is prepared by dissolving 0. 300 moles of cyanoacetic acid, , in sufficient water to make exactly one liter of solution. The in the resulting solution is 0. 032 m. what is the ionization (aq) Again, let"s abbreviate the weak acid as ha. = 3. 82x10 3: in a 0. 25 m solution of benzylamine, , the concentration of is 2. 4x10 3 m. what is the ionization constant for this weak base. Following as before lets abbreviate this weak base as, say, b for the neutral form and. K : (a) what are the concentrations of.
