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Quiz 1 Chem Bio Lesson 2 > Lesson 7: Precipitation and Volatilizatio Gravimetry > Flashcards

Lesson 7: Precipitation and Volatilizatio Gravimetry Flashcards

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1
Q

A substance that is dissolved in a solution

A

Solute

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2
Q

the liquid in which asoluteisdissolvedto form a solution.

A

Solvent

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3
Q

a solution that contains less than the maximum amount of solute that is capable of being dissolved

A

Unsaturated Solution

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4
Q

a solution that has dissolved as much solute as it is capable of dissolving

A

Saturated Solution

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5
Q

interaction between solute and solution that forms ionic bond or precipitate

A

Precipitate Forms

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6
Q

a solution that contains more than the maximum amount of solute that is capable of being dissolved at a given temperature.

A

Supersaturated Solution

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7
Q

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

A

supersaturated solution

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8
Q

a quantitative method that is based on determining the mass of a pure compound to which the analyte is chemically related.

It is based on mass measurements with an analytical balance

A

Gravimetric Methods

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9
Q

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.

A

Precipitation Gravimetry

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10
Q

the method in which the analyte is converted to a soluble precipitate

A

Precipitation Gravimetry

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11
Q

can be obtained by filtering, washing free of impurities, converting to a product of known composition by suitable heat treatment, and weighing.

A

precipitate

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12
Q

What are the 4 properties of precipitating agents

A

(1) easily filtered and can be washed free of contaminants
(2) of sufficiently low solubility that no significant loss of the analyte occurs during filtration and washing;
(3) Chemical inert or is unreactive with the constituents of the open atmosphere;
(4) Composition can be determined with high confidence after it was dried or ignited.

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12
Q

a few ions, atoms, or molecules (around four or five) come together to form a stable solid. Often, these nuclei form on the surface of suspended solid contaminants, such as dust particles.

A

Nucleation

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13
Q

two ways at which precipitates are formed

A

Nucleation and particle growth

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14
Q

If predominates, a precipitate containing a large number of small particles results

A

nucleation

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15
Q

if predominates, a smaller number of larger particles is produced.

A

particle growth

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15
Q

competition between additional nucleation and growth of existing nuclei

A

particle growth

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16
Q

minimum number of atoms, ions, or molecules join together to give a stable solid

A

Nucleation

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17
Q

As excess solute precipitates with time, supersaturation decreases to zero

A

supersaturated solution

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18
Q

coagulation of colloids can be hastened by what methods?

A
  1. Heating
  2. continuously stirring
  3. by adding an electrolyte into the mixture that will act as a medium
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19
Q

What is the reason for the stability of colloidal particles?

A

its particles are either positively or negatively charged and thus repel one another.

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20
Q

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

A

adsorption

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21
Q

retention of a substance within the pores of a solid.

A

absorption

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22
Q

random movement of solute in solution

A

Brownian Motion

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23
Q

Positive charge

A

Cation

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24
Q

negative charge

A

Anion

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25
Q

happens when colloids are washed, because during washing, some of the electrolytes responsible for keeping the coagulated form are leached from the internal liquid in contact with the solid particles.

A

Peptization

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26
Q

process by which a coagulated colloid reverts to its original dispersed state.

A

Peptization

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27
Q

How to prevent the the effect of increasing the volume of the counter-ion layer in peptization?

A

solvent that can easily volatilize is used for washing, so that during the drying step, this solvent is removed from the precipitates.

27
Q

What happens when electrolyte is removed in Peptization?

A

has the effect of increasing the volume of the counter-ion layer.

28
Q

are particles with diameters ranging from order of tenths of a millimeter or greater.

A

crystalline suspension

28
Q

of which the particles are too small (10-7 to 10-4( in diameter) that they are invisible to the naked eye.

A

colloidal suspensions

29
Q

suspended within the mixture, they show no tendency to settle thus making them difficult to filter

A

colloidal suspensions

30
Q

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

A

crystalline suspension

31
Q

the phenomenon in which the particles in a colloid scatter the beams of light that are directed at them

A

Tyndall effect

31
Q

Factors That Determine the Particle Size of Precipitates

A

Precipitate Solubility
Temperature
Reactant Concentrations
Rate At Which Reactants Are Mixed

32
Q

equation for relative supersaturation

A

Q-S / S

33
Q

What is meant by Q in the formula of relative supersaturation?

A

the concentration of the solute

34
Q

What is meant by S in the formula of relative supersaturation?

A

the equilibrium solubility

35
Q

if (q-s/s) is large, the precipitates will tend to be _____?

A

colloidal

35
Q

when (q-s/s) is small, then we can expect that the precipitates will be____?

A

crystalline in nature

36
Q

How to improved the particle size of a crystalline solid?

A

by minimizing Q or maximizing S, or both in equation.

37
Q

How to minimize Q the particle size of a crystalline solid ?

A

diluting the solution and adding the suitable precipitating agent slowly accompanied by good mixing should be done.

38
Q

a process in which a precipitate is heated in the solution from which it was formed (the mother liquor) and allowed to stand in contact with the solution.

A

Digestion

39
Q

How to maximize S the particle size of a crystalline solid?

A

S is increased by precipitating from hot solution or by adjusting the pH of the precipitation medium.

40
Q

the solution from which a precipitate was formed

A

Mother liquor

41
Q

a normally soluble compound is carried out of solution on the surface of a coagulated colloid.

A

Surface Adsorption

42
Q

often the major source of contaminants in coagulated colloids
but this problem doesn’t arise on crystalline precipitates.

A

Adsorption

42
Q

Explain how digestion improved the purity of many coagulated colloids.

A

water is expelled from the solid to give a denser mass that has a smaller specific surface area for adsorption

43
Q

How to improved the purity of many coagulated colloids?

A

Digestion

43
Q

This compound consists of the primarily adsorbed ion and an ion of opposite charge from the counter-ion layer.

A

Surface Adsorption

44
Q

the filtered solid is re-dissolved and reprecipitated

A

Reprecipitation

45
Q

water is expelled from the solid to give a denser mass that has a smaller specific surface area for adsorption.

A

Reprecipitation

46
Q

contaminant ions replace an ion in the lattice of a crystal

A

mixed crystal formation

46
Q

adds substantially to the time required for an analysis.

A

Reprecipitation

47
Q

Requirement for the exchange in Mixed-Crystal Formation

A

ions should have the same charge and their ionic sizes should differ in not more than 5%.

48
Q

When a crystal is growing rapidly during precipitate formation, foreign ions in the counter-ion layer may become trapped, or occluded, within the growing crystal.

A

Occlusion

49
Q

occurs when crystals lie close together during growth. Several crystals grow together and in so doing trap a portion of the solution in a tiny pocket.

A

Mechanical entrapment

50
Q

are at a minimum when the rate of precipitate formation is low, that is, under conditions of low supersaturation

A

occlusion and mechanical entrapment

51
Q

There are four types of coprecipitation:

A
  1. surface adsorption,
  2. mechanical entrapment,
  3. occlusion
  4. mixed-crystal formation
52
Q

a reaction that involves the simultaneous occurrence of nucleation, growth, coarsening, and/or agglomeration processes.

A

Coprecipitation

52
Q

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

A

Occlusion

53
Q

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

A

Coprecipitation

54
Q

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

A

Homogeneous precipitation

54
Q

Two types of Gravimetric Analysis

A

Precipitation Method and Volatilisation method

55
Q

may occur in both colloidal and crystalline precipitates, but occlusion and mechanical entrapment are confined to crystalline precipitates.

A

Mixed-crystal formation

56
Q

nvolve the generation of a precipitating agent from a chemical reaction carried out slowly.

A

Precipitation in homogeneous solutions

57
Q

are better suited for analysis than a solid formed by direct addition of a precipitating reagent.

A

both colloidal and crystalline

58
Q

analysis of an ion by measuring mass of a precipitate formed from the ion

A

Precipitation Method

59
Q

measuring mass before and after heating and removal of a volatile substance

A

Volatilisation method

Quiz 1 Chem Bio Lesson 2 (3 decks)

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