post lab discussion: exp. 7 Flashcards
a type of titration that involves the formation of precipitate
precipitation titration
when the titrant and analyte combine tgt, what does it create
insoluble material. it continues until all of the analytes have been consumed
true or false:
precipitation titration response rate is sometimes too slow
true
silver chloride precipitates out as a _____
white substances
in Mohr’s method of precipitation titration, what is the
titrant:
indicator:
titrant: AgNO3 (silver nitrate)
indicator: K2CrO4 (potassium chromate )
in Mohr’s method of precipitation titration, why does silver chromate should precipitate first
as it has much lower Ksp value in theory
Ksp
- measure how soluble a particular ionic solid is in water of another solvent
- the smaller the Ks, the less soluble
it uses a small quantity of K2Cr2O4
such that the chloride concentration is much higher than that of chromate. This causes AgCl to preferentially precipitate.
Mohr’s methpd
what is the endpoint of Mohr’s Method of Precipitation Titration
reddish rown color remains “stable” - does not disappear with stirring
this ions are more reactive than CrO4^2- so the Ag+ ions preferentially react with ____ ions first to form ____ before reacting with CrO4^2-
chloride ions
chloride ions
white ppt
what are the disadvantages of Mohr’s Method of Precipitation Titration
can only be carried out btwn pH of 7 and 10
in acidic environments, chromate (CrO4^2–) is converted to chromic acid which does not react with excess silver ions
what are the limitations of precipitation titration
very few halide ions can be titrated
coprecipitation also occurs
endpoint is very difficult to analyze
in Mohr’s Method of Precipitation Titration identify the
titrant:
analyte:
indicator:
endpoint:
titrant: AgNO3 (silver nitrate)
analyte: Cl- (chloride ions)
indicator: K2CrO4 (potassium chromate)
endpoint: reddish-brown ppt
