COMPLEXATION and PRECIPITATION TITRIMETRY
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Uses ___ for TITRATING CATIONS. These reagents are ORGANIC COMPOUNDS that contain several ___ that form mutiple COVALENT BONDS with METAL IONS
Complex-forming reagents electron-donor groups
___ is a positively charged ion, i.e. one that would be attracted to the ___ in electrolysis.
cation cathode
Most METAL IONS react with ____ to form COORDINATION COMPOUNDS or ___.
Electron-pair donors Coordination compounds/complexes
The DONOR SPECIES or ____ must have at least ___ or ___ available for BOND FORMATION
Ligand One pair Unshared electrons
The NUMBER OF COVALENT BONDS that a CATION(+) tends to FORM with ELECTRON DONORS is its ___
Coordination number
Typical values for coordination number (3)
two four six
TRUE or FALSE Species formed as a result of coordination can only be electrically neutral
FALSE They can be positive, neutral, or negative
TRUE or FALSE all nonmetal ions are found as COMPLEX IONS (a.k.a COORDINATION COMPLEXES)
FALSE ALMOST ALL METAL IONS are found as COMPLEX IONS
Parts of Complex ions / coordination complexes(3)
Ligand (outer) Metal Ion (center) ex. CO3+ Counter ion, for charge balance (Cl-)3
___ are TITRIMETRIC methods based on COMPLEX FORMATION Based upon a particular class of COORDINATION COMPOUNDS called ____
Complexometric methods Chelates
Chelate is produced when a metal ion coordinates with ___ to form a ___
two or more DONOR GROUPS of a SINGLE LIGAND FIVE- to SIX- membered HETEROCYCLIC RING
Types of ligands based on donor groups: (3 main)
Unidentate = 1 Bidentate = 2 Tridentate = 3 Tetradentate, Pentadentate, Hexadentate
What are the adventages of MULTIDENTATE over UNIDENTATE ligands? (2)
They generally REACT MORE COMPLETELY with CATIONS thus providing SHARPER END POINTS MULTIDENTATE ORDINARILY REACT with METAL IONS in a SINGLE STEP PROCESS (UNIDENTATES take TWO or MORE TERMEDIATE SPECIES)
Titrations with ___ TERTIARY AMINES (with N and lone pair) that contains ___ form STABLE CHELATES with many ___
Aminocarboxylic Acids Carboxylic acid groups metal ions
MOST widely used COMPLEXOMETRIC TITRANT has ___ POTENTIAL SITES for BONDING to a METAL ION; the ___ and __ It is a ___ ligand.
Ethylenediaminetetraacetic acid (EDTA) SIX FOUR CARBOXYL GROUPS TWO AMINO GROUPS HEXADENTATE LIGAND
Solutions of EDTA are particularly VALUABLE as TITRANTS because the EDTA combines with METAL IONS in a ____ RATIO REGARDLESS of the CHARGE on the CATION(+) Example, silver and aluminum complexes Ag^+ + Y^4- Al^3+ + Y^4-
1:1 RATIO Ag^+ + Y^4- = AgY^3- Al^3+ + Y^4- = AlY^-
Many CATIONS form ___ when the pH is RAISED to the level REQUIRED FOR SUCCESSFUL TITRATION w/ EDTA An ___ is NEEDED to keep the CATION in the solution
oxide precipitates (hydroxides, oxides, or oxyhydroxides) Auxillary complexing agent
Zinc (II) is usually titrated in a medium that has fairly fairly high concentrations of ___ and ___
Ammonia Ammonium Chloride
___ are usually ORGANIC dyes that form colored ___ with METAL IONS in a ___ range that is characteristic of a particular ___ and dye.
Indicators for EDTA titrations chelates pM cation
___ is typically a ___ indicator used in titration of several cCOMMON CATIONS but behaves as an ___ indicator. It forms ___ with more than TWO DOZEN metal ions. But only few are appropriate for END POINT DETECTION
Erichrome Black T metal-ion acid/bae Red complexes
MORDANT BLACK II components, color, and pH (4)
Erichrome Black T Solochrome Black T Blue pH=10
MUREXIDE vs MUREXIDE-CALCIUM COMPLEX color
Murexide Blue - Purple Murexide-Calcium complex - Red
____ is the total ___ and ___ concentration in a WATER SAMPLE and is EXPRESSED as the CONCENTRATION of ___.
Water Hardness calcium magnesium ion Calcium carbonate
Historically, WATER “HARDNESS was” defined in terms of the capacity of CATIONS in the water to REPLACE the ___ or ___ ions in SOAP This forms BARELY SOLUBLE products that cause SCUM in the sink or bathtub
sodium potassium