COMPLEXATION and PRECIPITATION TITRIMETRY Flashcards
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
