THE CHEMISTRY OF FIVE ANIONS

1
THE CHEMISTRY OF FIVE ANIONS
Purpose?
1) Explore different types of reactions via
observations. 2) Devise experimental method to
identify two unknown anions in a
mixture.
FIRST WEEK LAB
Test of reactivity via observations of all
possible combinations.
In groups of 3-4 devise experimental method to
identify a solution with 2 unknowns Work on net
ionic equations for reactions observed (pre-lab).
FIRST WEEK HOMEWORK
Turn in experimental method (each student) -
can be typed or yellow sheet - have a copy for
yourself to follow Group discussion of
methods Make revisions Carry out revised
methods to identify ions Group discussion of net
ionic reactions
SECOND WEEK LAB
2
Anions Reagents

1. Classes of ReactionsPrecipitation Acid/Base
   Oxidation/Reduction (redox) Complexation

• carbonate nitric acid
• oxalate cobalt (II) nitrate
• nitrite barium nitrate
• bromide sodium hydroxide
• hydrogen sulfate hydrogen peroxide/H
• (bisulfate)

acid/base, possible redox
complexation, ppt.
ppt.
acid/base
redox
3
Today Observations of Reactivity
Anions are in 1- mL dispensers.
Reagents are in bottles. (Do not waste.)
Add the reagent drop-wise Observe after
first few drops Observe after excess (mixed
well) If no reaction observed 2nd test
measure ?T 2 mL REAGENT, 1 mL ANION,
measure T before and after Demonstration
Common errors contaminated equipment
faulty recording of observations not
recording both drops excess results
illegible notebook
4
Next Week
Method Development in Groups before next class
Develop procedure to identify two anions in
mixture Flow Chart often works well Reagent
added Possible Observation Interpretation,
Conclusion, Next step Usually 3-4 tests
required to unambiguously identify anions Be
careful of possible interference from other
anion Record method in notebook (list group
members) Turn in yellow sheet/copy at beginning
of 2nd week along with pre-lab Presentation of
method/critique by class Individually carry out
revised experimental method Group works on Net
Ionic Equations Lab due beginning of lab period
of following lab experiment
5
M O N O D E N T A T E L I G A N D S
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Types of ligands
BIDENTATE LIGANDS. Form two bonds to the central
atom.
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EXTRA INFORMATION FOR 5 ANIONS EXPERIMENT         
                                                  
              
  Precipitation Acid/Base Redox Complexation
Definition/ Experimental Observables         formation of solids pH change temperature change rxn of known acid/base pairs   involves transfer of electrons involves changes in oxidation states reactions with O2, H2, or other known oxidizers or reducers complexes often colored  reaction of a transition metal with a ligand  
Additional Information (solubility rules on page 147-149 in Oxtoby, values of solubility product constants in Table 9-1, p. 405 in Oxtoby)  meaning of solubility product constants to be discussed later)   lists of common acids/bases and their pK's in Table 8-2, p.355 in Oxtoby)  meaning of pKa's to be discussed later lists of common strong oxidants and reductants on website, standard reduction potentials in Appendix E in Oxtoby -- meaning of standard reduction potentials to be discussed later discussion pp. 131-132, Oxtoby, examples of ligands given in Table 19-1, p. 811 and bidentate ligands in Fig. 19-2, p. 812 in Oxtoby