Portland State University - - Professor Carl C. Wamser

Chemistry 331 - Fall 1997

Pre-Quiz, Chapter 6



E-mail distributed over the class discussion list at noon on Friday, October 31 :

Chemistry 331 Pre-Quiz, Chapter 6 - Acids and Bases

return by e-mail to Dr. Wamser : WamserC@pdx.edu

due before 8 am, Wednesday, November 5, 1997

Refer to Table 6.1 in your text to determine relative acidities and basicities of the compounds mentioned below.

(1/2 point each part, 5 points total)

For each pair of rectants indicated below:
a) complete the acid-base reaction (use names for the products)
b) identify the acid and the base (among the reactants)
c) identify the conjugate acid and conjugate base (among the products)
d) predict whether the reaction is favored in the forward or reverse direction
e) calculate an equilibrium constant (for the forward reaction)

1. ethyllithium + ethanol -->

2. phenol + ammonia -->


ethyllithium + ethanol --> lithium ethoxide + ethane
(base) + (acid) --> (conj. base) + (conj. acid)

pKa (ethanol) = 15.9
pKa (ethane) = 48

favored in the forward direction (ethanol is the stronger acid)

pK = 48 - 16 = 32

K = 10^32


phenol + ammonia --> ammonium phenoxide
(acid) + (base) --> (conj. acid) + (conj. base)

pKa (phenol) = 9.95
pKa (ammonium) = 9.24

favored slightly in the reverse direction (ammonium is the stronger acid)

pK = 9.24 - 9.95 = -0.71

K = 10^ -0.71 = 0.2