Gravimetric Methods

Question 1

Quantitative methods that are based on determining the mass of a pure compound to which the analyte is chemically related.

Answer 1

Gravimetric Methods

Question 2

The analyte is separated from a solution of the sample as a precipitate and is converted to a compound of known composition that can be weighed.

Answer 2

Precipitation Gravimetry

Question 3

The analyte is separated from other constituents of a sample by converting it to a gas of known chemical composition

Answer 3

Volatilization gravimetry

Question 4

The mass of the gas then serves as a measure of the analyte concentration

Answer 4

Volatilization gravimetry

Question 5

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

Answer 5

Electrogravimetry

Question 5

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

Answer 5

Electrogravimetry

Question 6

The mass of this product then provides a measure of the analyte concentration.

Answer 6

Electrogravimetry

Question 7

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

Answer 7

Gravimetric Titrimetry

Question 8

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

Answer 8

Atomic mass spectrometry

Question 9

The concentration of the resulting ions is then determined by measuring the electrical current produced when they fall on the surface of an ion detector

Answer 9

Atomic mass spectrometry

Question 9

The concentration of the resulting ions is then determined by measuring the electrical current produced when they fall on the surface of an ion detector

Answer 9

Atomic mass spectrometry

Question 10

is converted to a sparingly soluble precipitate

Answer 10

Analyte

Question 11

Precipitate is then filtered, washed free of impurities, converted to a product of known composition by suitable heat treatment, and weighed

Answer 11

Precipitation Gravimetry

Question 12

Properties of Precipitates and Precipitating
Reagents

Answer 12

• Easily filtered and washed free of contaminants
• Sufficiently low solubility that no significant loss of the analyte occurs during filtration and washing
• Unreactive with constituents of the atmosphere of known chemical composition after it is dried or, if necessary, ignited

Question 12

Properties of Precipitates and Precipitating
Reagents

Answer 12

• Easily filtered and washed free of contaminants
• Sufficiently low solubility that no significant loss of the analyte occurs during filtration and washing
• Unreactive with constituents of the atmosphere of known chemical composition after it is dried or, if necessary, ignited

Question 13

particles show no tendency to settle from solution and are difficult to filter

Answer 13

Colloidal suspensions

Question 14

The particles of a ____ suspension tend to settle spontaneously and are easily filtered

Answer 14

Crystalline suspension

Question 15

Colloidal and suspension are influenced by

Answer 15

precipitate solubility, temperature, reactant concentrations, and the rate at which reactants are mixed

Question 16

are best precipitated from hot, stirred solutions containing sufficient electrolyte to ensure coagulation

Answer 16

Colloids

Question 17

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

Answer 17

digestion

Question 18

the solution from which a precipitate was formed

Answer 18

mother liquor

Question 19

The filterability of a coagulated colloid often improves if it is allowed to stand for an hour or more in contact with the hot solution

Answer 19

True

Question 20

Generally more easily filtered and purified than are coagulated colloids

Answer 20

Crystalline Precipitates

Question 21

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

Answer 21

Coprecipitation

Question 22

Compounds are removed from solution during precipitate formation

Answer 22

* Surface adsorption * Mixed-crystal formation * Occlusion * Mechanical entrapment

Question 23

A common source of coprecipitation and is likely to cause significant contamination of precipitates with large specific surface areas

Answer 23

Surface Adsorption

Question 24

the filtered solid is redissolved and reprecipitated.

Answer 24

Reprecipitation

Question 25

* A type of coprecipitation in which a contaminant ion replaces an ion in the lattice of a crystal

Answer 25

Mixed-Crystal Formation

Question 26

Type of coprecipitation in which a compound is trapped within a pocket formed during rapid crystal growth

Answer 26

Occlusion

Question 27

A process in which a precipitate is formed by slow generation of a precipitating reagent homogeneously throughout a solution

Answer 27

Homogeneous precipitation

Question 28

0* The temperature required to dehydrate a precipitate completely may be as low as ___ or as high as ___

Answer 28

100 degree celcius; 1000 deg. celcius

Question 29

no hydrogencarbons

Answer 29

Inorganic Precipitating Agents

Question 30

Typically form slightly soluble salts or hydrous oxides with the analyte

Answer 30

Inorganic Precipitating Agents

Question 31

Reagents that convert an analyte to its elemental form for weighing

Answer 31

Reducing Agents

Question 32

hydrogencarbons

Answer 32

Organic Precipitating Agents

Question 33

forms slightly soluble nonionic products

Answer 33

Coordination compounds

Question 34

Organic precipitating agents

Answer 34

* 1. Coordination compounds - forms slightly soluble nonionic products * 2. Forms products in which the bonding between the inorganic species and the reagent is largely ionic