Redox Titrimetric Methods Flashcards
Give the three most commonly oxiding titrants in redox methods.
Permanganate, dichromate, iodine
Give the two common reducing titrants in redox methods
Fe2+ and thiosulfate
The reaction of permanganate is in ___ medium.
Acidic
The reaction of permanganate is in ___ medium.
Acidic
In permanganimetry, the titration does not require an indicator since the oxidized (violet) and reduced (colorless) forms of titrant (MnO4-) differ in color. True or false
True
KMnO4 can be standardized in acidic medium using which of the ff.
A. Pure Fe wire
B. Sodium oxalate
C. Arsenic trioxide
ABC
At the beginning of the titration, the violet color of MnO4- persists for several seconds before it disappears. As Mn2+ is formed, the reaction proceeds more rapidly as a result of ______.
Autocatalysis
What is the endpoint of permanganimetry when an excess MnO4- has been added.
Faint pink color
n of C2O4^2-
2
n of MnO4-
5
Common oxidizing titrant weaker than permanganate, dichromate, and cerium
Iodine
Solutions of iodine lack ____ so they are standardized regularly
Stability
2 types of titrations that involves iodine. Which of the two is commonly performed?
Iodometry and Iodimetry.
Iodometry
________ refers to the direct use of iodine while ________ refers to the generation of iodine.
Iodometry, Iodometry
Process that involves the titration of an analyte (reducing agent) with solutions of iodine (oxidizing agent)
Iodimetry
Process of indirect determination of an analyte (oxidizing agent) shich is added to excess iodide to produce iodine, titrated with standard thisoulfate solution.
Iodometry
Forms when the molecular iodine complexes with iodine. It also forms a dark blue complex with the amylose units of starch
Triiodide ion (I-)
Triiodide io decomposes in solutions when the concentration of iodine is high.Thus ____ is added before nearing the endpoint, and addition of _____ is resumed until the end point is reached.
Starch, titrant (thiosulfate)
Solutions of ____ can be used in place of KMnO4- in most procedures as it’s also a strong oxidizing agent.
Ce4+
Solutions of Ce4+ can be prepared from the primary standard _____ in 1M H2S2O4
Diammonium hexanitratoacerate (IV)
(NH4)2[Ce(NO3)6]
In oxidation with cerium, Ce4+ prepared from other salts such as Ce(OH)4 must be standardized using ____
Iron or sodium oxalate
Ce4+ is _____ (in acid) and Ce3+ is ____. Yet cerium can’t serve as it’s own indicator because the color is not so distinct.
yellow, colorless
These are used to visually detect end points during redox titrations.
Redox indicators
What is the suitable indicator for Ce4+ when the primary standard used is Fe2+
Tris (1,10- phenanthroline) iron or ferroin
A relatively strong oxidizing agent, though weaker compared to permanganate and cerium
Potassium dichromate
Use of K2Cr2O7 as ______ is limited only to analytes that are highly oxidizable.
Oxidant
Which of the ff. are the advantages of using dichromate?
A. availability as primary standard
B. Long term stability of it’s solution
AB
The color of Cr2O7^2- is ______ and complexes of Cr3+ range from ______ to ______.
Orange, green to violet
True lr false. Dichromate can serve as it’s own indicator.
False
_______ whose oxidized form is ______ and reduced form is _____, giver very distict end point with Cr2O7^2-.
Diphenylamine sulfonic acid (C12H11NO3S)
Red-violet
Colorless
____ proposed ____ that relates the reduction potential (E) of an electrochemical reaction to the standard electrode potential (E°), temperature and activities (or concentrations) of the chemical species undergoing reduction and oxidation
Walther Nernst, Nernst Equation
By plotting the reduction potential of an electrochemical cell against the volume of titrant, ____ can be generated.
Titration curve
