NAME: September 26, 2008
OVER
Chemistry 231 – Elementary Organic Chemistry
In-Class Quiz -- #2
1. (6 pts. total; 3 pts. each) For each of the following questions, circle the BEST
answer.
a. Strongest Bronsted-Lowry acid
H
2
O H
2
S H
2
Se H
2
Te
b. Has the highest pK
a
CCl
3
CH
2
OH CBr
3
CH
2
OH CF
3
CH
2
OH CH
3
CH
2
OH
2. (4 pts) Carbonic acid, H
2
CO
3
, is a diprotic acid. That is, it can donate two protons.
In the space provided below, explain why the first acid dissociation of carbonic acid
(pK
a1
= 6.4) is greater than the second (pK
a2
= 10.3). You may find it helpful to use
a structural diagram.
Place your answer here
After the first ionization, there is a negative charge on the compound (this is
the bicarbonate anion). Removing a proton (H
+
) from a negatively charge ion
is more difficult due to Coulombic attraction. Hence, the pK
a
differences.
OC
O
OH
H
OC
O
O
H
OC
O
O
Bicarbonate
anion
