Gravimetric Methods of Analysis (PART 1) [Sir Jameso PPT]

Question 1

Gravimetric methods of analysis are based on determining the ______ of a pure compound to which the analyte is chemically related.

Answer 1

mass

Question 2

There are two major types of gravimetric methods:

Answer 2

precipitation methods and volatilization methods.

Question 3

In _________, the analyte is converted to a sparingly soluble precipitate.

Answer 3

precipitation gravimetry

Question 4

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

Answer 4

precipitation gravimetry

Question 5

In ___________, the analyte or its decomposition products are volatilized at a suitable temperature.

Answer 5

volatilization gravimetry

Question 6

The volatile product is then collected and weighed, or, alternatively, the mass of the product is determined indirectly from the loss in mass of the sample

Answer 6

volatilization gravimetry

Question 7

The ideal precipitating reagent would react with the analyte to give a product that is

1. Readily filtered and washed free of ______
2. Of sufficiently _________ so that no significant loss of the solid
   occurs during filtration and washing
3. Unreactive with constituents of the __________
4. Of known composition after it is dried or, if necessary, ________

Answer 7

contaminants
low solubility
atmosphere
ignited

Question 8

Precipitates made up of ____ are generally desirable in gravimetric work because large particles are easy to filter
and wash free of impurities.

Answer 8

large particleslarge particles

Question 9

a solid made up of particles having diameters that are less than 10-4 cm.

Answer 9

colloid

Question 10

It show no tendency to settle from solution, nor are they easily filtered.

Answer 10

Colloidal particles

Question 11

The particles, with dimensions on the order of tenths of a millimeter or greater, temporarily dispersed in the liquid phase is called a _________

Answer 11

crystalline suspension

Question 12

The particles of a ________suspension tend to settle spontaneously and are readily filtered.

Answer 12

crystalline

Question 13

the concentration of the solute at any instant and S is its equilibrium solubility.

Answer 13

Q

Question 14

What Factors Determine Particle Size?

When (Q - S)/S is large, the precipitate tends to be _____

Answer 14

colloidal

Question 15

What Factors Determine Particle Size?

When (Q - S)/S is small, a ______ is more likely.

Answer 15

crystalline solid

Question 16

How Do Precipitates Form?

Assume that precipitates form in two ways, namely by ______and by ________

Answer 16

nucleation
particle growth

Question 17

How Do Precipitates Form?

The particle size of a freshly formed _____________is determined by which way is faster.

Answer 17

precipitate

Question 18

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

Answer 18

Nucleation

Question 19

the individual particles of most colloids to give a filterable, amorphous mass that will settle out of solution.

Answer 19

Coagulate, or agglomerate

Question 20

It can be hastened by heating, stirring, and adding an electrolyte to the medium.

Answer 20

Coagulation

Question 21

a process in which a substance (gas, liquid, or solid) is held on the surface of a solid.

Answer 21

Adsorption

Question 22

In contrast, ______involves retention of a substance within the pores of a solid.

Answer 22

absorption

Question 23

a process by which a coagulated colloid returns to its dispersed state.

Answer 23

Peptization

Question 24

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

Answer 24

Coprecipitation

Question 25

a common source of coprecipitation that is likely to cause significant contamination of precipitates with large specific
surface areas, coagulated colloids.

Answer 25

Surface Adsorption

Question 26

A drastic but effective way to minimize the effects of adsorption is reprecipitation, or double precipitation.

Answer 26

Reprecipitation

Question 27

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

Answer 27

Occlusion

Question 28

_______ entrapment occurs when crystals lie close together during growth.

Answer 28

Mechanical

Question 29

is often remarkably helpful in reducing these types of coprecipitation.

Answer 29

digestion

Question 30

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

Answer 30

Homogeneous precipitation

Question 31

After filtration, a _______ is heated until its mass becomes constant.

Answer 31

gravimetric precipitate

Question 32

Some precipitates are also ________to decompose the solid and form a compound of known composition.

Answer 32

IGNITED

Question 33

This new compound is often called the

Answer 33

weighing form

Question 34

Recording thermal decomposition curves is often called _____ or thermogravimetric analysis, and the mass vs. temperature curves are called ______________.

Answer 34

thermogravimetry
thermograms

Question 35

Numerous ______ reagents have been developed for the gravimetric determination of inorganic species.

Answer 35

organic

Question 36

One forms slightly soluble nonionic products called ________

Answer 36

coordination compounds.

Question 37

The other forms products in which the bonding between the inorganic species and the reagent is __________ ionic

Answer 37

largely

Question 38

cyclical metal-organic compounds in which the metal is a part of one or more five- or six-membered rings.

Answer 38

Chelates

Question 39

_______ and _________are two widely used chelating reagents.

Answer 39

8-Hydroxyquinoline
dimethylglyoxime

Question 40

__________ tetraphenyl borate is a near-specific precipitation agent for potassium and ammonium

Answer 40

Sodium

Question 41

is spectacular in appearance since it has a beautiful vivid red color

Answer 41

Nickel dimethylglyoxime

Question 42

is an important example of an organic precipitating reagent that forms salt-like precipitates

Answer 42

Sodium tetraphenylborate, (C6H5) 4BNa+

Question 43

The two most common gravimetric methods based on volatilization are
those for ____and carbon dioxide.

Answer 43

water
carbon dioxide.

Question 44

are ordinarily decomposed by acids to give carbon dioxide, which is readily evolved from solution by heat.

Answer 44

Carbonates