Potentiometry Parts 1 and 2

Question 1

What’s an anode?

Answer 1

Electrode where oxidation occurs

Question 2

What’s a cathode?

Answer 2

Electrode where reduction occurs

Question 3

What is a phase boundary and what is its denotation?

Answer 3

Phase boundary indicates the boundary between two phases in a solution (i.e.: solid-liquid interface) and it is indicated by one vertical line “|”

Question 4

What is a salt bridge and what is its denotation?

Answer 4

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 “||”

Question 5

What is the purpose of the salt bridge?

Answer 5

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

Question 6

True or False: Galvanic cell is a spontaneous system

Answer 6

True

Question 7

What reaction does a > 1 cell potential give?

Answer 7

Electrolytic cell, a non-spontaneous chemical reaction

Question 8

What is a standard potential?

Answer 8

Measure of the driving force for a reaction

Question 9

What is a standard potential?

Answer 9

Measure of the driving force for a reaction

Question 10

What electrolyte system is on the left-hand side of a cell notation?

Answer 10

The anode

Question 11

What is a Platinum black electrode (Pt)?

Answer 11

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

Question 12

True or False: SHE is convenient to use in laboratory experiments

Answer 12

False: Other reference electrodes such as SCE (Saturated calomel electrode) is used instead

Question 13

What is the Nernst equation?

Answer 13

The relationship between the cell potential to the chemical concentration

Question 14

(Nernst equation) At equilibrium, Q\_\_K and the potential is \_\_\_
A. > ; positive
B. < ; negative
C. = ; 0
D. < ; positive
E. = ; negative

Answer 14

C. = ; 0

At equilibrium, Q=K and the potential is 0

Question 15

What is Potentiometry?

Answer 15

The use of electrode potentials to determine analyte concentrations

Question 16

What are Inert electrodes?

Answer 16

Inert electrodes respond to redox couples without participating directly in the reaction

Question 17

What reagent is in the buret of a redox titration?

Answer 17

Oxidation reagent

Question 18

What reagent is in the beaker of a redox titration?

Answer 18

Reducing reagent

Question 19

What are standard oxidizing and reducing agents?

Answer 19

Strong, standardized oxidizing/reducing agents

Question 20

What is the equivalence point?

Answer 20

Amount of titrant = amount of analyte

Question 21

What is the endpoint?

Answer 21

Observed change that approximately signals the equivalence point

Question 22

How can you determine the endpoint of a titration?

Answer 22

Through tracking changes in potential (pH probe) and Redox indicator dyes (phenolphthalein)

Question 23

What does pre-treatment do to samples for redox titrations?

Answer 23

Converts all species to the same oxidation state

Question 24

What is used to pre-treat ions?

Answer 24

Auxillary reducing agents such as solid metal and stannous chloride

Question 25

What are some examples of oxidizing agents?

Answer 25

Bismuthate, Peroxydisulfate, Hydrogen peroxide

Question 26

For standard reducing agents, what can E° tell you?

Answer 26

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

Question 27

Standard oxidizing agents have _______ E° value

Answer 27

Large

Question 28

What does the Nernst equation indicate?

Answer 28

Tells us what to expect for a titration curve

Question 29

Instead of electrochemical cells, what indicator can be used for redox titrations?

Answer 29

Reagents that undergo half-cell reactions with an associated colour change