Ch 17 Complexation and Precipitation Reactions and Titrations

Question 1

In the formation of complexes, what do you call the donor species that has at least one pair of
unshared electrons available for bond formation

Answer 1

ligand

Question 2

Common inorganic ligands:

Answer 2

Water, ammonia, and halide ions

Question 3

is an ion or a molecule that
forms a covalent bond with a cation
or a neutral metal atom by donating a
pair of electrons, which are then shared
by the two

Answer 3

ligand

Question 4

The number of covalent bonds that a cation tends to form with electron donors
is its

Answer 4

coordination number

Question 5

Titrations based on complex formation, sometimes called

Answer 5

complexometric titrations

Question 6

is produced when a metal ion coordinates
with two or more donor groups of a single ligand to form a five- or six-membered
heterocyclic ring

Answer 6

chelate

Question 7

A ligand that has a single donor group, such as ammonia, is called single-toothed or

Answer 7

unidentate

Question 8

A ligand that has a two donor group, such as glycine

Answer 8

bidentate

Question 9

comes from the Latin word
dentatus and means having toothlike
projections

Answer 9

Dentate

Question 10

Another important type of complex is formed between metal ions and cyclic
organic compounds, known as

Answer 10

macrocycles

Question 11

macrocyclic compounds that form three
dimensional cavities that can just accommodate appropriately sized metal ions.

Answer 11

cryptands

Question 12

Are pH-dependent equilibrium constants
that apply at a single pH only. Commonly used when the complex compound formed are pH dependent

Answer 12

conditional formation constant

Question 13

In these titrations, a
metal ion reacts with a suitable ligand to form a complex, and the equivalence point
is determined by an indicator or an appropriate instrumental method.

Answer 13

complexometric titrations.

Question 14

Usually in complexometric titrations, the ligand is the ________, and the metal ion is the ______

Answer 14

titrant, analyte

Question 15

Titration that is based on reactions that yield ionic compounds of limited solubility

Answer 15

Precipitation titrations

Question 16

Titrations with silver nitrate, the most widely used and important precipitating reagent, are sometimes called

Answer 16

argentometric titrations

Question 17

titration curves for precipitation reactions is consist of a plot of

Answer 17

pAg (y-axis) vs. volume of the silver reagent (x-axis)

Question 18

The 3 End Points for Argentometric Titrations

Answer 18

Chemical, potentiometric, and amperometric end points

Question 19

the potential difference between a silver electrode and
a reference electrode is measured as a function of titrant volume

Answer 19

potentiometric titrations

Question 20

the current
generated between a pair of silver electrodes is measured and plotted as a function of
titrant volume

Answer 20

amperometric titrations

Question 21

The ______________is one of the most common argentometric methods. In this method, silver ions are titrated with a standard solution of
thiocyanate ion, where Iron(III) serves as the indicator. The solution turns red with the first slight excess of
thiocyanate ion due to the formation of Fe(SCN)^2+.

Answer 21

Volhard method

Question 22

An argentometric titration, wherein sodium chromate serves as the indicator of chloride, bromide, and cyanide ions. Silver ions react with chromate to form the brick-red silver chromate (Ag2CrO4)
precipitate in the equivalence-point region.

Answer 22

Mohr method

Question 23

The ________________ uses an adsorption indicator, an organic compound that
adsorbs onto or desorbs from the surface of the solid in a precipitation titration. Ideally, the adsorption or desorption occurs near the equivalence point and results not
only in a color change but also in the transfer of color from the solution to the solid
or vice versa.

Answer 23

Fajans method

Question 24

these are the stable complexes, produce by organic complexing agents, that bind a metal and prevent interferences

Answer 24

masking agents

Question 25

Who recognized tertiary amines that remarkably form stable chelates with many metal ions

Answer 25

Gerold Schwarzenbach

Question 26

most widely used complexometric titrant

Answer 26

EDTA/ Ethylenediaaminetetraacetic acid

Question 27

the six potential sites of EDTA for bonding a metal ion:

Answer 27

four carboxyl groups and the two amino groups, each of the latter with an unshared pair
of electrons.

Question 28

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.

Answer 28

1:1

Question 29

EDTA and other similar chelating agents are often called because of their ability to remove or inactivate metal
ions

Answer 29

sequestering
agents

Question 30

must be used in EDTA titrations to prevent
precipitation of the analyte as a hydrous oxide. Such reagents cause the end points to be less sharp.

Answer 30

auxiliary complexing
agents

Question 31

a typical metal-ion organic dyes that form colored chelates with metal ions, where the metal complexes form are generally red. It behaves as an acid/base indicator as well as a metal-ion indicator for EDTA Titrations.

Answer 31

Eriochrome Black T

Question 32

What are the Titration Methods Involving EDTA

Answer 32

Direct Titration:
Methods Based on Indicators for the Analyte.
Methods Based on Indicators for an Added Metal Ion.
Potentiometric Methods.
Spectrophotometric Methods

Back Titration:
Displacement Methods

Question 33

In ____________, an unmeasured excess of a solution containing the magnesium or zinc complex of EDTA is introduced into the analyte solution

Answer 33

displacement titrations

Question 34

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

Answer 34

masking agent

Question 35

A magnesium ion indicator that decomposes less than eriochrome black T

Answer 35

Calmagite