MODULE 2: 1-6

Question 1

The relationship between chemical reactions and electricity

Answer 1

ELECTROCHEMISTRY

Question 2

movement of electrons

Answer 2

ELECTRICITY

Question 3

involve movement of electrons

Answer 3

CHEMICAL REACTIONS

Question 4

X loses electrons

Answer 4

Reducing agent

Question 5

A process in which one substance or molecule is reduced & another is oxidized

Answer 5

REDOX REACTION

Question 6

Devices that use a chemical reaction to create electricity

Answer 6

GALVANIC CELL OR VOLTAIC CELL

Question 7

Example of Galvanic/Voltaic Cell

Answer 7

Battery

Question 8

positive electrode

Answer 8

anode

Question 9

negative electrode

Answer 9

cathode

Question 10

Metals that are usually solid

Answer 10

Neutral Metals

Question 11

Metals that dissolve in water

Answer 11

DISSOCIATED METALS

Question 12

Decrease in cell potential caused by the operation of the cell (current flow)

Answer 12

POLARIZATION

Question 13

2 Forms of Polarization

Answer 13

1. Concentration polarization
2. Activation polarization/Hydrogen polarization/Cathodic Polarization

Question 14

Decrease in cell potential, which results from changes in concentrations of the ions in the electrolytic solutions

Answer 14

Concentration Polarization

Question 15

The rate of redox reaction (electron movement) _____ as it reaches saturation.

Answer 15

decreases

Question 16

The layer of adsorbed atomic hydrogen is said to polarize the cell.

Answer 16

ACTIVATION/HYDROGEN/CATHODIC POLARIZATION

Question 17

Both concentration and activation polarization ____ the net oxidation-reduction (REDOX) reaction rate.

Answer 17

decrease

Question 18

In corrosion processes, ______ usually has the greater effect.

Answer 18

activation polarization

Question 19

All metals (except for ___, ____, and ____)
exist naturally in combined forms as ___, non-metals, semi-metals.

Answer 19

gold, platinum, palladium, metal

Question 20

Metals in combined form are called as ___

Answer 20

MINERALS

Question 21

Combined forms
OCCSS

Answer 21

1. Oxides
2. Carbonates
3. Chlorides
4. Sulfides
5. Sulfates

Question 22

____ as a process is exactly the reverse of the extraction materials.

Answer 22

Corrosion

Question 23

___is the deterioration or degradation of a material due to interaction with its environment.

Answer 23

Corrosion

Question 24

Loss of useful properties due to corrosion

Answer 24

*weakening of metallic material

*metal becomes brittle (lesser malleable, lesser ductile)

*decaying of surface

Question 25

Types of metal corrosion

Answer 25

1. Dry or Chemical Corrosion 2. Wet or Electrochemical Corrosion

Question 26

Oxidation of metal **by oxygen or by other gases**

Answer 26

Dry or Chemical Corrosion

Question 27

Oxidation of metal exposed to an **aqueous** environment

Answer 27

Wet or Electrochemical Corrosion

Question 28

The ___ of metals is the **oxidation step** of the overall redox reaction.

Answer 28

wet corrosion

Question 29

During oxidation half-step, the cations or dissociated metals may:

Answer 29

1. **Dissolve** into solution 2. Combine with available anions or water **to form IONIC COMPOUNDS/HYDRATED OXIDES**

Question 30

The more ___ the electrode potential is, the ___ is the tendency for the pure metals to oxidize.

Answer 30

negative, higher

Question 31

___ is the process whereby the surface of a metal undergoes a SLOW, relatively uniform, removal of material

Answer 31

GENERAL CORROSION

Question 32

2 required conditions for Gen. Corrosion to occur

Answer 32

1. Metal is **exposed to a moisture/aqueous** environment. 2. **Chemical reaction** bet. metal and aqueous solution **to form an oxide**

Question 33

compound containing **oxygen**

Answer 33

OXIDE

Question 34

Water is an _____

Answer 34

ampholyte

Question 35

Capable of reacting chemically as either acid or base. Said to be **amphoteric**.

Answer 35

AMPHOLYTE

Question 36

____ and ____ lead to preferential removal of metal from certain parts of the surface.

Answer 36

Impurities, imperfections

Question 37

The corrosion cells, changing as surface and solution differences change, cause ____.

Answer 37

GENERAL OVERALL CORROSION

Question 38

**rare** iron oxide, **BLACK**-colored powder, confused with **RUST**, consists of hydrated iron oxide

Answer 38

Iron (II) Oxide or FERROUS OXIDE (FeO)

Question 39

**DARK RED**, called as **rust**. Builds up on FeO layer

Answer 39

Iron (III) Oxide or Ferric Oxide (Fe2O3) **HEMATITE**

Question 40

plus 3 oxidation state

Answer 40

FERRIC IRON (Fe3+)

Question 41

plus 2 oxidation state

Answer 41

**FERROUS IRON (Fe2+)**

Question 42

contains O2-, Fe2+, Fe3+, BLACK powder

Answer 42

Iron (II, III) Oxide OR **Ferroferric Oxide (Fe3O4)** **MAGNETITE**

Question 43

metal does **not** become **active** in the corrosion reaction

Answer 43

PASSIVITY

Question 44

most desirable oxide layer, adheres best on the metal

Answer 44

FE3O4

Question 45

Metals that **form thin, tenacious oxide films** when exposed to atmosphere

Answer 45

ZIRCONIUM, CHROMIUM, ALUMINUM, STAINLESS STEEL

Question 46

Factors affecting General Corrosion Rate

Answer 46

1. Temperature 2. Water velocity 3. Oxygen 4. pH 5. Metal surface condition and composition 6. Dissolved solids

Question 47

Substances (like O2) that **remove** the adsorbed atomic hydrogen

Answer 47

DEPOLARIZERS

Question 48

*FeO is **SOLUBLE***, oxide dissolves as it is formed. Metal is in direct contact w/ acid solution

Answer 48

pH < 4.0

Question 49

Corrosion rate is relatively **independent of pH** of the solution

Answer 49

pH 4 - 10

Question 50

corrosion rate is **observed to fall** as **pH is INCREASED**

Answer 50

pH > 10

Question 51

*@ high temp*, corrosion rate is **HIGH**, pH goes **LOWER**

Answer 51

pH < 4.0

Question 52

*@ high temp*, corrosion rate is **lower** as pH value **increases**

Answer 52

pH bet. 4 and 12

Question 53

*@ high temp*, corrosion rate **increases**

Answer 53

pH beyond 12

Question 54

Plant pH to prevent corrosion

Answer 54

pH 9 and 11

Question 55

another factor affecting General corrosion rate

Answer 55

exposure **TIME** of metals to corrosive environment