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Lecture 14

CHEM 212 Lecture Notes - Lecture 14: Equivalence Point, Titration Curve, Analyte

Course Code
CHEM 212
Hamilton M.Coreen

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Chem 212!
Lecture 14!
Oct. 14/2016!
Precipitation Titrations:!
-not collecting the precipitate!
"-dont have to take the time to make a really good quality ppt!
Volumetric Analysis:!
-volume is the data!
-Titration= addition of measurments of a reagent solution!
-Titrant- reagent solution (known conc)!
-Indicator- observable property (colour) that changes NEAR the equivalence point!
"-NEAR bc how good are these indicators--> picking an indicator that changes colour near pH of your end """"""
-Automated titrater !
-Equivalance point: when quantity of titrant is added in exact amount needed for stoichiometric rxn with analyte.
True end of titration!
-Endpoint- where indicator changes colour.!
-reaction must be fast and complete!
-2 ways to find endpoint:!
"-Colour indicator!
"-Measure a signal while doing the titration, keep going until signal doesn't change any more then plot signal""""
" on y axis vs volume of titrant and find endpoint graphically.!
2 Types of methods:!
-Direct titration- add titrant from buret until run complete!
-Back titration- add a known amount of reagent to the analyte!
"""-let them react!
"""-then titrate the leftover of the 1st reagent with a 2nd reagent!
Amount of analyte= amount of 1st reagent-amount of second reagent!
"-use when reaction is not fast or is not easy to find the end point!
Precipitation Titration Curve!
-The titrant is X and pX is the amount of X left in solutions-not the total amount of X added as some is used to
make the ppt.!
-all titration curves look the same because they use a log function!
-ion selective electrodes!
-only pH electrode will give you pH reading!
-when you want o measure pH you must calibrate the meter!
*when precipitating one comes from left hand one comes from right hand, there is no X=X relationship*!
At the equivalence point there is a relationship between reactants and titrant--> ONLY PART OF TITRATION where
there is a relationship--> SET UP ICE TABLE!
-Before and after and at the equivalence point all have dierent calculations!
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