1
Last Time
•
Reaction quotient – Q
p
and Q
c
– Mathematical Relation to K
c
and K
p
– Q < K forward
:
Q > K reverse
– Omit solids in heterogeneous systems
•
Equilibrium from initial conditions
– Molar proportions
– Equilibrium tables
Equilibrium Tables
aA
→
bB
A
B
Initial concentration
[A]
[B]
Change in conc.
–ax
+bx
Equilibrium conc.
[A] – ax
[B] + bx
•
Use the definition for K
c
and solve for x
•
Sign of x determined by Q and K
←
Example – Using “x”
K
c
= 54.6 at 700 K for the reaction of hydrogen
with iodine gas to form HI(g).
Suppose that
38.4 g of HI, 5.0 g of H
2
, and 26.8 g of I
2
are
placed together in a 2 L container at this
temperature.
What are the concentrations of
each substance at equilibrium?
Example
At 294.8 K, K
c
is 1.2x10
–4
for the decomposition
of NH
4
HS(s).
Calculate the equilibrium
concentrations of NH
3
(g) and H
2
S(g) when a
solid sample of NH
4
HS(s) is allowed to
decompose to equilibrium at 294.8 K.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
2
Le Chatelier’s Principle
•
Equilibrium adjusts to release stress
•
Explains changes in reactions due to
– n – number of moles used
This is the end of the preview.
Sign up
to
access the rest of the document.
 Winter '08
 Clemens
 Chemistry, Thermodynamics, Equilibrium, Reaction, Chemical reaction, Kc, Exothermic

Click to edit the document details