Complex-Formation Titration

Question 1

a sample in solution is titrated with a standard solution of a ligand to form a colored complex in the presence of an indicator until the endpoint is reached

Answer 1

Complex-Formation Method / Complexation Titrimetry / Complexometric Titration

Question 2

species with a least one unshared pair of electrons available for bond formation (e.g. H2O, NH3, X2, and most metal ion in water).

Answer 2

Ligand

Question 3

yield complex ions or coordination compounds (product formed when a cation bonds with an electron donor species
based on its coordination number

Answer 3

Complex-Formation Method / Complexation Titrimetry / Complexometric Titration

Question 4

produced when a metal ion coordinates with single ligand with one donor group

Answer 4

Complex

Question 5

produced when a metal ion coordinates with single ligand with two or more donor groups

Answer 5

Chelate

Question 6

used in the assay of substances containing metals

Answer 6

Complex-Formation Method / Complexation Titrimetry / Complexometric Titration

Question 7

determination of hardness of water (ppm)

Answer 7

Complex-Formation Method / Complexation Titrimetry / Complexometric Titration

Question 8

substances that render metals in the sample inactive

Answer 8

Masking agent

Question 9

Examples of masking agent

Answer 9

Triethanolamine, Thioglycols, Potassium cyanide, Ammonium fluoride

Question 10

masking agent that suppress Al-EDTA in presence of Mg-EDTA

Answer 10

Triethanolamine

Question 11

masking agents that inactivate Hg and Cu, to allow titration of Zn at pH 6

Answer 11

Thioglycols

Question 12

masks metals like Co, Ni, Cu and Zn

Answer 12

Potassium cyanide

Question 13

masks Ca, Mg and Al, to allow titration of Zn

Answer 13

Ammonium fluoride

Question 14

Examples: titration of Bi at pH 2, titration of Ca at pH 13

Answer 14

Adjusting the pH of solution

Question 15

Bi is titrated at what pH?

Answer 15

2

Question 16

Ca is titrated at what pH?

Answer 16

13

Question 17

binds the metal cation being determined in complexometric analyses

Answer 17

Standard solutions serve as a ligand

Question 18

EDTA by nature is what?

Answer 18

inorganic

Question 19

8-hydroxyquinoline by nature is what?

Answer 19

organic

Question 20

how many donor groups does glycine have?

Answer 20

2 - bidentate

Question 21

how many donor groups does EDTA have?

Answer 21

6 - hexadentate

Question 22

Tetradentate aminopolycarboxylic acid standard solution

Answer 22

Nitrilotriacetic acid (NTA)

Question 23

Second most common complexing agent used in titrimetry

Answer 23

Nitrilotriacetic acid (NTA)

Question 24

Aminopolycarboxylic acid stadard solution and an ether analog of EDTA

Answer 24

Ethyleneglycol bis(B-aminoethylether)-N,N,N’,N’-tetraacetic acid (EGTA)

Question 25

Selectively titrates Ca in the presence of Mg ions

Answer 25

Ethyleneglycol bis(B-aminoethylether)-N,N,N’,N’-tetraacetic acid (EGTA)

Question 26

Hexadentate aminopolycarboxylic acid standard solution that is very stable dilute solutions but it is very sensitive to pH and may be selective with reactivity with metal ions

Answer 26

Ethylenediamine tetra acetic acid (EDTA)

Question 27

Commercially available in reagent quality as a free acid (H4Y) or as a dihydrate sodium salt (Na2H2Y·2H2O)

Answer 27

Ethylenediamine tetra acetic acid (EDTA)

Question 28

primary standard of EDTA

Answer 28

CaCO3

Question 29

indicator used in EDTA

Answer 29

eriochrome black T (EBT)

Question 30

usually employed in residual titrations

Answer 30

Zinc sulfate (ZnSO4)

Question 31

indicator used in zinc sulfate

Answer 31

dithizone

Question 32

are also ligands that binds metal ions effectively and prevents its precipitation, but can still be given up when EDTA is added

Answer 32

Auxiliary Complexing Agents

Question 33

It permits multiple metal to be titrated in alkaline solution with EDTA

Answer 33

Auxiliary Complexing Agents

Question 34

is the process of determining the conc. of metals in the presence of another metal

Answer 34

masking

Question 35

is a complexing agent that reacts selectively with a component in a solution to prevent that component from interfering in a determination

Answer 35

masking agent

Question 36

an auxiliary agent that preferentially forms complex with potentially interfering ions

Answer 36

masking agent

Question 37

permits titration of Mg and Ca ions in the presence of Cd, Co, Cu, Ni, Zn, and Pd as the these metals will form stable CN-1 complexes

Answer 37

KCN (cyanide ion)

Question 38

will provided sufficient alkalinity to prevent complexation of Al-EDTA in the presence of Mg-EDTA — allowing Mg determination

Answer 38

Triethanolamine (TEA — C6H15NO3)

Question 39

It allows complexation of Zn at pH 6 by inactivation Hg and Cu which interacts with sulfhydryl groups (-SH) in the --- molecule.

Answer 39

Thioglycols

Question 40

masks Ca, Mg, and Al to allow titration of Zn.

Answer 40

Ammonium fluoride (NH4F)

Question 41

Any of these three can be used to mask Sb in an analyte solution

Answer 41

Ascorbic acid, Citrates, and Tartrates

Question 42

Direct EDTA Titrations (3)

Answer 42

Calcium, Magnesium and Zinc

Question 43

Residual EDTA Titrations (2)

Answer 43

Aluminum and Bismuth

Question 44

One of the oldest and most widely used indicator exclusive at pH 7-11; ideal for Mg titrations, but not for Ca

Answer 44

Eriochrome Black T (EBT)

Question 45

Wine red color (complexed) and turns blue color (free) at the endpoint

Answer 45

Eriochrome Black T (EBT)

Question 46

Oxidized slowly by dissolved oxygen; ascorbic acid is used to retard oxidation or solid EBT is added directly prior to titration

Answer 46

Eriochrome Black T (EBT)

Question 47

structurally similar to EBT; with better stability in aqueous solutions

Answer 47

calmagite

Question 48

an excellent indicator for EDTA titrations with the rare earth metals. It can resist the presence of small amount of Fe+3 during Ca and Mg titrations

Answer 48

Arsenazo I

Question 49

Ca-sensitive and can be used for Ca determination from biological samples. It can also be used for Uranium and Thorium determination

Answer 49

Arsenazao III

Question 50

commonly used in a tetrasodium salt form and can be used in acidic solutions. It will appear red (complexed) and turns yellow (free) at the endpoint

Answer 50

Xylenol Orange

Question 51

deep blue color at endpoint

Answer 51

Hydroxynaphthol blue

Question 52

rose pink color at endpoint

Answer 52

Dithizone