Gravimetric Analysis Flashcards
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.
Precipitation gravimetry
the analyte is separated from
other constituents of a sample by
conversion to a gas The weight of
this gas then serves as a measure
of the analyte concentration
Volatilization gravimetry
In volatization gravimetry, the sample is converted to what?
Gas
What serves as a measure of the analyte concentration in volatization gravimetry?
Weight of escaped gas
the analyte is separated by deposition on an
electrode by an electrical current
Electrogravimetry
an electric conductor that makes contact with the nonmetallic circuit parts of a circuit, such as an electrolyte, semiconductor, or vacuum
Electrode
Method of thermal analysis in which changes in
physical and chemical properties of materials are measured as a function of increasing temperature or as a function of time.
Thermogravimetry
refers to process in solution with excess amount of solute
Supersaturation
a substance that causes the precipitation of a specified substance.
Precipitant
Whose tiny particles are invisible to the
naked eye (10-7 to 10-4 cm in diameter)
Colloidal particle
Particles visible to the naked eye
Crytalline solid
Which particle settles down spontaneously
Crystalline solid
Known as the Oswald Ripening
Digestion of precipitate
involves dissolution of small particles
and reprecipitation on larger ones resulting in
particle growth and better precipitate
characteristics.
Digestion
process by which a coagulated colloid reverts to
its original dispersed state in case of colloidal
precipitates
Peptization
In this, the precipitate is
converted to a more chemically stable form
Drying and ignition
The ideal precipitating reagent would react
__________ or at least ___________
Specifically, selectively
Which type of precipitate is ideal?
Crystalline
T or F: ideal precipitate are of sufficiently low solubilty
True (so it doesnt dissolve and it can be filtered)
an unstable solution that contains a higher solute concentration than a saturated solution.
Supersaturated solution
In relation to Ksp and Qsp, when can precipitation happen
Ksp > Qsp
Relation of precipitation and supersaturation
Inversely proportional (kapag mataas ang supersaturation ibig sabihin marami ang solute. these solute can be formed into precipitate and when they do, bumababa ang saturation. gets???)
a process of forming smaller particles or colloidal particles.
Nucleation
The initial formation process in which
a minimum number of atoms, ions, or molecules join
together to give a stable solid.
Nucleation
The subsequent growth after
nucleation; building up of formerly formed nuclei
Particle growth
Two ways to control RSS and increase particle growth
- Increase equilibrium solubility
- Decrease solute concentration
says that particles collide but do
not interact. It is not affected by gravity
Brownian movement
Which type of precipitate is Brownian Movement applied?
Colloids
Refers to accumulation and build up
Coagulation
Involves a combination of larger group of many different ions/atoms with each other
Agglomeration
Which particles are stable?
Colloids
Why are colloids stable?
It has negative and positive chargue
Refers to the mainly absorbed ions on the surface
Primary adsorption level
Contains sufficient excess of negative ions to balance the charge on the primary adsorption layer
Counter-ion layer
This layer prevents interaction
with the same kind of particle due to the
presence of the negative ions found within
this layer.
Counter-ion layer
thought as a measure of the repulsive force that the particle exerts on like particles in the solution.
Effective charge
Diameter of colloids
10^-7 to 10^-4 cm
Characteristics of colloids
Suspended
Characteristics of crystalline
Settled from the solution (filterable)
Diameter of crystalline partices
> 10^-4 cm
Relationship of nucleation, RSS, and particle size
High RSS = High nucleation = Small particles
Relationship of particle growth, RSS, and particle size
Small RSS = High particle growth = Large particles
Relationship between equilibrium solubility and RSS
High RSS, low solubility (they can’t be soluble because it’s supersaturated na)
Therefore, to lower RSS is to increase solubility
Relationship between RSS and concentration
High RSS, high concentration (concentration of solute is high because it’s supersaturated)
Therefore, to lower RSS is to decrease the concentration
These are precipitants that creates complex
ions.
Complexing agents
A process in which a substance (gas,
liquid, or solid) is held on the surface
of a solid.
Adsorption
A process in which a substance
within the pores of a solid.
Absorption
generally more easily filtered and purified
than coagulated colloids.
Crystalline
improves the purity and filterability of
both colloidal and crystalline precipitates. It
makes the precipitate pure as impurities and
contaminants are removed when filtered.
Digestion
a process in which normally soluble compounds
are carried out of solution by a precipitate and
may result in impurities and/or contamination
Coprecipitation
a process by which a foreign compound
precipitates on top of the desired precipitate.
Post precipitation
The impurity is chemically or physically adsorbed
onto the surface of precipitates
Surface adsorption
the major source of contamination
in coagulated colloids but of no significance in
crystalline precipitates.
Adsorption
A type of coprecipitation in which a contaminant
ion replaces an ion in the lattice of a crystal.
Mixed crystal formation
type of coprecipitation in which a compound
(foreign ions in the counter-ion layer) is physically
trapped within a precipitate during rapid
precipitate formation.
Occlusion
T or F: Occlusion involve particles of same charge while Mixed Crystal formation doesnt
False (baliktad)
A type of coprecipitation in which coprecipitated
physically trap a pocket of solution within a
precipitate during rapid precipitate formation.
Mechanical entrapment
a process in which a
precipitate is formed by slow generation of a
precipitating reagent homogeneously throughout a
solution
Homogenous precipitation
done by adding an
agent. A chemical added to a mixture which will
block any impurity from affecting the chemical
analysis
Masking
