Untitled - Kelly Walsh High School

288 CHEMISTRY FOR THE UTTERLY CONFUSED
Be Careful!
In order to do a problem involving the formation of a complex ion requires you
to know the value of x. While x is usually either 4 or 6, it can have other values.
How can you tell what x is? You must have additional information. Your instructor
or textbook may tell you directly what x will be. In other cases, you may need
to examine a table of formation constants, K f. If you see, for example, K f for
[Fe(C 2O 4) 3] 3 is equal to some value, the subscript “3” tells you that x 3.
To change the general equation to a specific equation entails a simple substitution
of the formulas. Using [Fe(C 2O 4) 3] 3 as an example, we see that M Fe 3
and L C 2O 4 2 , to give the equation:
Fe 3 (aq) 3 C 2O 4 2 (aq) K [Fe(C2O 4) 3] 3 (aq)
This leads to the following equilibrium constant expression:
Kf [Fe(C2O4 )3
3 ]
[Fe3 2 3 ][C2O4 ]
Make sure you move the ion charges inside the bracket so they are not mistaken
for exponents.
Once you have the correct equilibrium constant expression, there is no difference
in solving the complex ion equilibrium than any other equilibrium problem.
In considering the properties of the elements, hydrogen is usually an exception.
It can form compounds with both metals and nonmetals. Metals react with nonmetals
to form cations. Metals conduct electricity through conduction bands,
partially filled bands described by the application of Molecular Orbital theory
to multi-atom systems. Metals follow the general periodic trends in properties.
Nonmetals form anions when reacting with metals. Nonmetals also follow the
general periodic trends. Transition metals may adopt more than one oxidation
state. Transition metals may also form coordination compounds. The groups
attached to the transition metal are ligands.
1. Which element is nearly always an exception?
2. What is the oxidation state of hydrogen when it combines with a metal?
3. What is the oxidation number of Os in OsO 4?
4. Which elements form superoxides?
5. Metals above hydrogen on the Activity Series react with acids to produce
what gas?