Potentiometry Parts 1 and 2 Flashcards
What’s an anode?
Electrode where oxidation occurs
What’s a cathode?
Electrode where reduction occurs
What is a phase boundary and what is its denotation?
Phase boundary indicates the boundary between two phases in a solution (i.e.: solid-liquid interface) and it is indicated by one vertical line “|”
What is a salt bridge and what is its denotation?
A salt bridge is a connection between the two solutions, one with the anode and the other with a cathode. It is denoted by two vertical lines “||”
What is the purpose of the salt bridge?
Prevents direct mixing of the two electrolyte solutions to force the electrons to travel through the voltmeter. Salt bridges also completes the circuit and keeps the beaker electrically neutral. This is done by using a tube with a porous frit
True or False: Galvanic cell is a spontaneous system
True
What reaction does a > 1 cell potential give?
Electrolytic cell, a non-spontaneous chemical reaction
What is a standard potential?
Measure of the driving force for a reaction
What is a standard potential?
Measure of the driving force for a reaction
What electrolyte system is on the left-hand side of a cell notation?
The anode
What is a Platinum black electrode (Pt)?
It can act both as a cathode or an anode in a reaction. It is bubbled at 1 atm of H2 (g) to maintain saturated solution, but it (Pt) is not part of the reaction itself. The Pt will act as an anode if the half-cell potential is positive, or will act as a cathode if half-cell reaction is negative
True or False: SHE is convenient to use in laboratory experiments
False: Other reference electrodes such as SCE (Saturated calomel electrode) is used instead
What is the Nernst equation?
The relationship between the cell potential to the chemical concentration
(Nernst equation) At equilibrium, Q\_\_K and the potential is \_\_\_ A. > ; positive B. < ; negative C. = ; 0 D. < ; positive E. = ; negative
C. = ; 0
At equilibrium, Q=K and the potential is 0
What is Potentiometry?
The use of electrode potentials to determine analyte concentrations
What are Inert electrodes?
Inert electrodes respond to redox couples without participating directly in the reaction
What reagent is in the buret of a redox titration?
Oxidation reagent
What reagent is in the beaker of a redox titration?
Reducing reagent
What are standard oxidizing and reducing agents?
Strong, standardized oxidizing/reducing agents
What is the equivalence point?
Amount of titrant = amount of analyte
What is the endpoint?
Observed change that approximately signals the equivalence point
How can you determine the endpoint of a titration?
Through tracking changes in potential (pH probe) and Redox indicator dyes (phenolphthalein)
What does pre-treatment do to samples for redox titrations?
Converts all species to the same oxidation state
What is used to pre-treat ions?
Auxillary reducing agents such as solid metal and stannous chloride
What are some examples of oxidizing agents?
Bismuthate, Peroxydisulfate, Hydrogen peroxide
For standard reducing agents, what can E° tell you?
Lower E° value means it is a better reducing agent (and the other way around) while lower E° value means it is a better oxidizing agent
Standard oxidizing agents have _______ E° value
Large
What does the Nernst equation indicate?
Tells us what to expect for a titration curve
Instead of electrochemical cells, what indicator can be used for redox titrations?
Reagents that undergo half-cell reactions with an associated colour change
