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AnaChem > (F) Gravimetric method of analysis > Flashcards

(F) Gravimetric method of analysis Flashcards

1
Q

Based on measuring the mass of a pure compound though which the analyte is chemically related.

A

Gravimetric Analysis

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2
Q

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

A

Precipitation Gravimetry

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3
Q

analyte is separated from other constituents by conversion to gas, and the weight of the gas is used as a measure of analyte concentration

for substances thar evaporate or are volatile

A

volatilization gravimetry

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4
Q

analyte is separated by deposition on an electrode via electrical current

A

Electrogravimetry

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5
Q

changes in physical and chemical properties of materials are measured as a function of increasing temperature or as a function of time

A

Thermogravimetry

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6
Q

T of F : You’re supposed to wash colloidal precipitates like crystalline precipitates

A

F you do NOT wash them because peptization occurs

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7
Q

The conversion of precipitate into colloidal solution by adding a suitable electrolyte

A

peptization

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8
Q

T or F : it is not ideal to have low solubility in a precipitate

A

false it is ideal so that your precipitate won’t dissolve as you are filtering it

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9
Q

T or F : it is ideal that your precipitate is free of contaminants and be bigger in size

A

T

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10
Q

T or F : The more reactive your precipitate is the better

A

False it is better if it is stable and unreactive with the constituents of the atmosphere

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11
Q

The net effect of these variables that determine the particle size can be accounted for relating the particle size to a single property

A

relative supersaturation by von weimarn, 1925

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12
Q

unstable solution that contains a higher solute concentration than a
saturated solution. As excess solute precipitates with
time, supersaturation decreases to zero.

A

supersaturated solution

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13
Q

T or F : if Ksp > Qsp = precipitation will not happen

A

F it will

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14
Q

T or F : If supersaturation decreases to zero, precipitation
will also stop.

A

T

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15
Q

measure of the solute’s
supersaturation.

A

Q - S
Q= concentration of the solute
Idk what the S is i cant find it sorry

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16
Q

T or F: The relationship between the value of RSS and the
particle size is DIRECTLY PROPORTIONAL. As the
value of RSS increases, the particle size decreases, and
vice versa.

A

F (inversely)

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17
Q

process of forming smaller particles or colloidal
particles.

A

NUCLEATION.

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18
Q

T or F: The RSS value is BIG . A solution must have a low
supersaturation which would mean that the precipitate will be larger in terms of the particles.

A

F (its smol like my brein)

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19
Q

The initial formation process in which
a minimum number of atoms, ions, or molecules join
together to give a stable solid.

A

NUCLEATION

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20
Q

2 types of nucleation

A

sponataneous and induced

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21
Q

The subsequent growth after
nucleation. It means building of nuclei over each other
which will eventually form a crystalline solid.

A

PARTICLE GROWTH:

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22
Q

are precipitants that creates complex
ions.

A

(Complexing
agents

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23
Q

happen when you add
an organic precipitant in the solution and
creates complexes with the metallic ion.

A

Complex ions

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24
Q

metallic ion will be
part of the central atom/structure of the
precipitate and around the central atom/metallic ion, there will negative charges
contributed by the organic complexing agent.
It increases solubility of precipitate as well.)

A

Complexes

25
Q

T or F : We use a concentrated solution in a precipitating process

A

False we dont

26
Q

Tor F; To decrease Q , we use the homogeneous precipitation technique

A

T

27
Q

This is when particles collide but do
not interact. It is not affected by gravity.

A

Brownian movement

28
Q

does not settle out of solution due to its size and Brownian movement

A

Colloids

29
Q

Accumulation and building up

A

coagulation

30
Q

same as coagulation but involves a combination of a larger froup of different ions/ atoms with each other

A

Agglomerate

31
Q

T or F: coagulation may be hastened by cooling, digestion and adding an electrolyte

A

F (it will be hastened by heating in a water bath, stirring, and adding an electrolyte)

32
Q

T or F :Colloids are stable due to being either a negative and positively charged particles

A

T

33
Q

components of electric double layer

A

primary adsorption layer and counter ion layer

34
Q

a layer in the electric double layer that consists mainly of adsorbed silver ions

A

primary

35
Q

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

A

ADSORPTION

36
Q

A process in which a substance
within the pores of a solid.

A

ABSORPTION

37
Q

a layer in the electric double layer that contains sufficient
excess of negative ions (principally nitrate) to just
balance the charge on the surface of the particle.

A

counter - ion layer

38
Q

T or F : as colloid particles approach each other, the electric double layer produces an electrostatic force, preventing panicles from adhering or colliding

A

T

39
Q

measure of repulsive force that particle exerts on like particles in the solution

A

Effective charge (q)

40
Q

T or F : More diluted means that there is more distance for forces of agglomeration

A

F less distance

41
Q

T or F : Increased heat decreases absorbed ions

A

F increases

42
Q

these are bigger particles, easily filtered and are purer

A

Crystalline

43
Q

T or F : Crystalline formation can be improved significantly by minimizing Q and maximizing S in the RSS value or von weirman equation

A

T

44
Q

T or F: effective charge should be reduced to zero to increase repulsive forces, making it easier to coagulate

A

F (decreases repulsive force)

45
Q

main cause of impurities -
process where normally soluble compounds are carried out of solution by a precipitate and may result in impurities and / or contamination

A

coprecipitation

46
Q

process where a foreign compound precipitates on top of the desired precipitate

A

post precipitation

47
Q

major source of contamination in coagulated colloids du to impurity being chemically or physically adsorbed on the surface of precipitates

A

surface adsorption

48
Q

T or F: by using volatile electrolytes, this increases surface adsorption

A

false decrease

49
Q

occurs when exchange of two ions that have the same charge, roughly about the same size (>5%), belongs to the same crystal class

A

mixed crystal formation

50
Q

T or F: changing to a more selective precipitating agent reprecipitation minimizes mixed crystal formation

A

T

51
Q

Greatest type of co-precipitation ni which a compound (freign ions in the counter-ion layer) is physically trapped within a precipitate during rapid precipitate formation

A

Occlusion

52
Q

A type of co-precipitation in which coprecipitates physically trap a pocket of solution within a precipitate during rapid precipitate formation.

A

Mechanical Entrapment

53
Q

process which a precipitate is formed by slow generation of a precipitating reagent homogeneously throughout a solution (therefore excesses do not occur)

A

Homogeneous Precipitation

54
Q

T or F : Solids formed by homogeneous precipitation are purer but smaller in size

A

F (larger)

55
Q

complexing agent, increasing purity and decreases the unwanted compounds / contaminants

A

urea

56
Q

reagents that form coordination compounds
and prevents formation of unwanted side products

A

chelating agents

57
Q

special type of ligand that can form multiple bonds to the metal ion resulting to a highly stable compound, highly colored coordination

A

chelates

58
Q

bonds to the central metal ion, donates electrons to the metal ion (chelating agents)

A

ligands

59
Q

creates complexes / chelates with nickel ion
normally forms red complex solution (cherry red) light green to dark red precipitate
can be enhanced by turning it slightly basic (add basic solns 8-10)

A

Dimethylglyoxime

AnaChem (9 decks)

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