Chapter 12 Test 2

Front 1

Gravimetric methods

Back 1

methods that depend upon measuringmass

Front 2

Precipitation methods

Back 2

The species to be determined isprecipitated by a reagent that yields a sparingly soluble product (a product of known composition, or a product that can beconverted to one of known composition).ȗ;�OAg�

Front 3

Volatilization methods

Back 3

theanalyte is separated from other sample constituents by converting it to a gasof known composition. The analyte (or its decomposition products) arevolatilized at a suitable temperature. The volatilized species are collectedand weighed directly or weighed by difference.

Front 4

Electrogravimetry

Back 4

The analyte is separated by deposition on an electrode by an electrical current

Front 5

gravimetric Titrimetry

Back 5

the mass of a reagent of known concentration required to completely react with the analyte provides the information needed to determine the analyte concentration

Front 6

Atomic mass spectrometry

Back 6

uses a mass spectrometer to separate the gaseous ions formed from the elements making up a sample of matter

Front 7

The idealprecipitating agents is one that reacts with one and only oneanalyte to produce as solid that is ...

Back 7

Low in solubility

easily filterable

Unreactive to the atmosphere

of known composition

large particle sizes work best

Front 8

Colloidal Suspensions

Back 8

Suspension whose particles are invisible to the naked eye 10-7 to 10-4

Front 9

Colloid

Back 9

Consist of solid particles with diameters that are less than 10-4 in size

Low solubilities

best precipitated from hot stirred solutions

Front 10

Crystalline suspension

Back 10

particles bigger in size and are easier to settle and are readily filterable

Front 11

Tyndall Effect

Back 11

movie example.

When particles scatter visible radiation

Front 12

Particle size of a precipitate is influenced by

Back 12

precipitate solubility

temperature

reactant concentrations

rate at which the reactants are mixed

Front 13

Relative supersaturation

Back 13

The net effect of all the variables that can be qualitatively accounted for

Q (concentration of solute)- S (equilibrium solubility) / S (equilibrium solubility)

Front 14

Large/ High Relative Supersaturation corresponds to

Back 14

Colloidal precipitate

Nucleation Mechanism

Large number of small products formed

Front 15

Small Relative Supersaturation

Back 15

Crystalline Sold precipitate

Particle Growth Mechanism

Small number of larger particles

Front 16

supersaturated solution

Back 16

an unstable solution that contains a higher solute concentration than a saturated solution

Front 17

Nucleation

Back 17

Process in which a minimum number of atoms, ions, or molecules join together to give a stable solid.

If dominates a large number of small particles results

Formation in a supersaturated solution of the smallest precipitate particles capable of spontaneous growth

Front 18

Particle Growth

Back 18

Deposition of ions/ molecules on the surface of the solid nucleated particles

If dominates, a small number of larger molecules results

Front 19

Adsorption

Back 19

The process in which a substance is held on a surface of a solid

Front 20

Absorption

Back 20

retention of a substance within the pores of a solid

Front 21

Coagulation/ Agglomerarion

Back 21

the process by which colloidal particles coalesce to form larger aggregates

Can be hastened by heating, stirring, and adding an electrolyte to the medium

Increasing particle size

Front 22

Colloidal suspensions are stable because

Back 22

all of the particles are positively or negatively charged

Front 23

Primary adsorption

Back 23

Charged layer of ions on the surface of a solid

Front 24

Counter Ion Layer

Back 24

Layer that surrounds the charged particle layer that consists of an excess of negative ions to balance the charge on the surface of the particle

Front 25

Electric Double Layer

Back 25

layer formed of the primary layer and the counter ion layer that provides stability to the colloidal suspension

Front 26

Increasingthe electrolyte concentration hasthe effect of decreasing the volume of the counter ion layer, thereby

Back 26

increasing the chances for coagulation

Front 27

Peptization

Back 27

the process by which a coagulated precipitate is returned to is colloidal state

Front 28

Peptization can be caused by

Back 28

Washing away electrolytes responsible for coagulation, increase the volume of the counter ion layer

Washing away colloidal pieces of the precipitate

Front 29

Peptization can be minimized by

Back 29

Washing a precipitate with a solution of an electrolyte that is volatilized during an ensuing drying step

Front 30

Digestion

Back 30

the process in which a precipitate is heated in the solution from which it was formed and allowed to stand in contact with the solution

expels water from the crystal producing a denser better filtering precipitate

Front 31

Mother Liquid

Back 31

the solution from which a precipitate is formed

Front 32

Co-precipitation

Back 32

process in which normally soluble compounds are carried out of a solution by a precipitate

Front 33

4 types of Co-precipitation

Back 33

Surface Adsorption

Mixed crystal formation

occlusion

Mechanical Entrapment

Front 34

Surface adsorption (equilibrium process)

Back 34

Causes contamination of precipitates with large surface areas like coagulated colloids

Front 35

Specific surface area

Back 35

The surface are per unit mass

Front 36

Mechanical entrapment (kinetic)

Back 36

when two crystals grow together and trap a species in the space between them

Front 37

Occulsion (kinetic)

Back 37

A compound is trapped within a pocket formed during rapid crystal growth

Front 38

Mixed Crystal Formation (equilibrium)

Back 38

co precipitation formed when one of the ions in the crystal lattice are replaced by an ion of another element

Front 39

Reprecipitation

Back 39

used to minimize adsorption

process by which the the filtered solid is redissolved and re precipitated

Lower contaminant concentration

Front 40

Co-precipitation is reduced by

Back 40

Using dilute solutions

Rapid filtration

Removing undesired ions before precipitaion

Front 41

Post precipitation

Back 41

Theprecipitate causes a localized high concentration of unwanted species.

Front 42

Drying

Back 42

removesthe solvent(s) of the mother liquid from which the precipitate was formed.

Front 43

Ignition

Back 43

converts the precipitate to a known composition called the weighing form.

Front 44

Homogenous precipitation

Back 44

Technique in which a precipitating agent is generated in a solution of the analyte by a slow chemical reaction

Front 45

Thermogravimetric analysis

Back 45

substance is heated and its mass is measured as a function of temperature.

Front 46

Coordination compounds

Back 46

species formed when between metal ions and electron pair donating groups.

Front 47

Chelating agents

Back 47

Substances with multiple sites available for coordinate bonding with metal ions.

products called chelates