FINALS 3: GRAVIMETRIC METHOD Flashcards
analysis consists of isolating from the
sample the constituent to be determined in its pure state
and weighing it accurately
GRAVIMETRIC ASSAY
How to identify/isolate the sample?
precipitating/precipitation
electrolysis
converting the substance to a gas
it determines the charge of the sample and this process is called?
electrolysis
characteristic of a precipitate
low solubility
Large in particle
Easily filtered
Pure and stable
Laws applied on precipitation
❖ Solubility product principle
❖ Law of Mass Action
❖ Common Ion effect
The ionic product exceeds the solubility product constant,
precipitation will occur
Solubility product principle
If there is an excess of one ion over the other, the
solubility of the precipitate will decrease
The common ion effect
For a system in equilibrium, any change in the factors such as
_______,_________,_______
the system will shift the equilibrium so as to counteract the effect
pressure
temperature
molar concentrations of the components,
The rate of the reaction is directly proportional to the product of the
molecular concentrations of the reacting substance
Law of mass action
6 Steps manufacturer do before Gravimetric Analysis:
1) Drying: by removing the debris
2) Preparation of Solution: adding a precipitating agent
3) Precipitation
4) Filtration
5) 2nd drying and Ignition
6) weight the sample
Gravimetric method by precipitation:
❖ Dissolve sample
❖ Add precipitating reagent
❖ Filter
❖ Dry
❖ Weigh
The residue weighed must have a _______ and ________.
(1) definite chemical composition
(2) bears a definite relation with the constituent to be determined.
Factor are also called as ?
chemical factor
calculation factor
conversion factor
equivalent factor
gravimetric factor
Defined as the weight of the constituent determined or sought
and is equivalent to the unit weight of a given substance.
Factor
Gravimetric Formula to find the percentage amount of an analyte?
W x CF x 100
% = ————————-
wt of sx
