ELECTROCHEMISTRY AND CORROSION

Question 1

USUALLY DEFINED
AS THE DEGRADATION OF METALS
DUE TO AN ELECTROCHEMICAL
PROCESS

Answer 1

corrosion

Question 2

One in which electricity is
produced by a chemical reaction.

Answer 2

electrochemical process

Question 3

a chemical reaction
involving the transfer of electrons
between two electrodes in an
electrochemical cell

Answer 3

electrochemical process

Question 4

These are also called Galvanic cells or simply
Voltaic cells

Answer 4

electrochemical cell

Question 5

s a device that converts
chemical energy produced in a redox reaction
into electrical energy

Answer 5

electrochemical cell

Question 6

Electrochemical cells are a combination of two electrical conductors known as _________ immersed in an __________

Answer 6

electrode, electrolyte

Question 7

he galvanic cell is named after

Answer 7

Luigi Galvani

Question 8

EChemical cell is composed of two compartments or

Answer 8

half cells

Question 9

On _______________, positive current flows through the metallic path
from positive electrode to negative electrode.

Answer 9

short-circuiting

Question 10

the gain of electrons or a
decrease in oxidation state by a
molecule, atom, or ion

Answer 10

reduction

Question 11

the loss of electrons or an
increase in oxidation state by a
molecule, atom, or ion

Answer 11

oxidation

Question 12

device used in an
electrochemical cell for connecting
its oxidation and reduction half
cells wherein an inert electrolyte is
used.

Answer 12

salt bridge

Question 13

junction that connects the
anodic and cathodic
compartments in a cell or
electrolytic solution

Answer 13

salt bridge

Question 14

The more _________ the reduction potential, the more these elements
want to attract electrons
towards them.

Answer 14

positive

Question 15

The energy conversion is
achieved by __________ redox reactions, producing a
flow of electrons in electrochemical cells.

Answer 15

spontaneous (ΔG <0)

Question 16

In __________, electrical energy is used to drive
a non-spontaneous (ΔG ≥ 0)
chemical reaction (redox
reactions)

Answer 16

electrolytic cell

Question 17

Types of electrochemical cells

Answer 17

Dissimilar Electrode Cell
Concentration Cell
Differential Temperature Cell

Question 18

These cells involve
different types of metals
or metal compositions
coming into contact,
leading to electron
transfer between them.

Answer 18

Dissimilar Electrode Cell

Question 19

Types of concentration cells

Answer 19

Salt concentration
Differential aeration

Question 20

These are cells with two identical
electrodes, each in contact with a
solution of different composition.

Answer 20

Salt concentration cell

Question 21

Occurs due to differences in potential
between differently Aerated areas
Part of the metal exposed to air is more
oxygenated and acts as a Cathode
Part of the metal immersed in the
electrolyte is poorly oxygenated & acts
as an anode

Answer 21

Differential aeration cells

Question 22

This is the type of cell when
two identical electrodes are
immersed in same
electrolyte, but the electrodes
are immersed into solution of
two different
temperatures

Answer 22

Differential temperature cell

Question 23

The _____________ series s has been established by measuring
the potential of various electrodes versus ____________

Answer 23

Electrochemical, standard hydrogen electrode (SHE)

Question 24

orderly arrangement of the
standard potentials for all metals.

Answer 24

Emf Series

Question 25

The more ________ values correspond to the more reactive metals

Answer 25

negative

Question 26

It arises when two metals with dissimilar compositions come into contact in the presence of an electrolyte.

Answer 26

Galvanic cell

Question 27

Determines the electrochemical potential and nobility of metals (and metal alloys)

Answer 27

Galvanic series

Question 28

Ranking of metals and alloys according to their free corrosion potential in a given electrolyte.

Answer 28

Galvanic series

Question 29

THE CLOSER A METAL OR AN ALLOY IS IN THE GALVANIC SERIES, THE __________ ARE THE EFFECTS OF GALVANIC CORROSION COMPARED TO THOSE METALS FAR APART.

Answer 29

LESS

Question 30

Conditions for Galvanic Corrosion

Answer 30

1. Metals involved must establish electrical connectivity 2. Metals must maintain ionic connectivity

Question 31

Current is produced when electrons flow (through anode to cathode)

Answer 31

Electrode potentials

Question 32

Types of reference electrode potentials

Answer 32

Standard Hydrogen Electrode Calomel Reference Electrode Silver-Silver Chloride Reference Electrode Saturated Copper-Copper Sulfate Reference Electrode

Question 33

Standard Electrode Potential (E = 0) at temperature of ______

Answer 33

278K

Question 34

The half cell reaction of SHE can be written as follows:

Answer 34

2H+ + 2e- <-> H2

Question 35

The reaction for SHE generally takes place on a

Answer 35

platinum electrode

Question 36

The pressure of the hydrogen gas present in this half cell for SHE is

Answer 36

1 bar

Question 37

Why Platinum is Used?

Answer 37

1. Relatively inert 2. . Has catalytic qualities 3. Surface can be platinized platinum electrode 4. Improve kinetics

Question 38

Reference electrode used in laboratory

Answer 38

Calomel reference electrode

Question 39

For CRE, _________ is placed at the bottom of the tube, which is covered with a paste of ____________

Answer 39

Pure mercury, mercury-mercurous chloride

Question 40

The calomel is only ___________ in potassium chloride solution

Answer 40

slightly soluble

Question 41

The half cell reaction of CRE can be written as

Answer 41

Hg2Cl2 + 2e- -> 2Hg + 2Cl-

Question 42

The activity of Hg22+, depends on the _________

Answer 42

concentration of KCl

Question 43

Composed of a silver wire, sometimes coated with a layer of solid silver chloride, immersed in a solution that is saturated with potassium chloride and silver chloride.

Answer 43

Silver-Silver Chloride Reference Electrode

Question 44

When the silver – silver chloride electrode is immersed in a chloride solution, the following equilibrium is established

Answer 44

AgCl + e- -> Ag + Cl-

Question 45

Like the calomel electrode, the potential in Silver-AgCl RE is more active the _____

Answer 45

HIGHER the KCl concentration

Question 46

In 0.1 N KCl for Ag-AgCl, the value is ________, and the temperature coefficient is__________

Answer 46

0.288 V; -4.3 × 10− 4 V/ ° C.

Question 47

Consists of metallic copper immersed in saturated copper sulfate.

Answer 47

Saturated Copper-Copper Sulfate Reference Electrode

Question 48

It is used primarily in field measurements where the electrode must be resistant to shock and where its usual large size minimizes polarization errors.

Answer 48

Saturated Copper-Copper Sulfate Reference Electrode

Question 49

The electrode's precision, though slightly lower than that of calomel or silver chloride electrodes, is still sufficient for most corrosion studies

Answer 49

Saturated Copper-Copper Sulfate Reference Electrode

Question 50

Half cell reaction for Cu-CuSO4

Answer 50

Cu2+ + 2e- -> Cu (0.316V, 7E-4)

Question 51

relate the current of an electrochemical reaction to the number of moles of the element being reacted and the number of moles of electrons involved.

Answer 51

Faraday’s empirical laws of electrolysis

Question 52

The charge carried by 1 mol of electrons is known as

Answer 52

1 faraday (F) = 96,485 C/mol

Question 53

It is the current produced in an electrochemical cell during corrosion. It is the dissolution current at the corrosion potential.

Answer 53

CORROSION CURRENT

Question 54

It is the speed at which any given metal deteriorates or corrodes in a specific environment

Answer 54

CORROSION RATE

Question 55

provides a way to calculate corrosion rate.

Answer 55

Corrosion current

Question 56

However, corrosion current alone doesn't directly tell you the____________

Answer 56

rate of material loss

Question 57

A reduction current that occurs when electrons flow from the electrode surface to a species in solution. For example, oxygen reduction in a fuel cell

Answer 57

CATHODIC CURRENT

Question 58

An oxidation current that occurs when electrons flow into the electrode from a species in solution. For example, hydrogen oxidation in a fuel cell

Answer 58

ANODIC CURRENT

Question 59

The absolute equality between the anodic and cathodic currents expressed below does not mean that the current densities for these currents are equal

Answer 59

SURFACE AREA EFFECT

Question 60

the effect of a certain amount of anodic current concentrated on a small area of metal surface will be __________ than when the effect of the same amount of current is dissipated over a much larger area

Answer 60

much greater

Question 61

If Sc/Sa >> 1, then __________. If Sc/Sa << 1, then ________

Answer 61

amplifying factor, stifling factor

Question 62

When polarization occurs mostly at the cathode, the corrosion rate is said to be

Answer 62

cathodically controlled

Question 63

occurs when the electrolyte resistance is so high that the resultant current is not suffi cient to appreciably polarize anodes or cathodes

Answer 63

Resistance control

Question 64

can be calculated from the corrosion potential and the thermodynamic potential

Answer 64

Corrosion current

Question 65

impressed current cathodic protection (ICCP) or by another metal that corrodes more readily than the metal being protected and therefore is sacrificed is the process

Answer 65

THEORY OF CATHODIC PROTECTION

Question 66

If the metal is polarized slightly beyond the open -circuit potential, φA , of the anode, the corrosion rate remain

Answer 66

zero

Question 67

Should the applied current fall below that required for complete protection, some ____________________ occurs

Answer 67

degree of protection