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Alawi_CHEMISTRY > MODULE 2: 1-6 > Flashcards

MODULE 2: 1-6 Flashcards

1
Q

The relationship between chemical reactions and electricity

A

ELECTROCHEMISTRY

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2
Q

movement of electrons

A

ELECTRICITY

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3
Q

involve movement of electrons

A

CHEMICAL REACTIONS

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4
Q

X loses electrons

A

Reducing agent

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5
Q

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

A

REDOX REACTION

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6
Q

Devices that use a chemical reaction to create electricity

A

GALVANIC CELL OR VOLTAIC CELL

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7
Q

Example of Galvanic/Voltaic Cell

A

Battery

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8
Q

positive electrode

A

anode

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9
Q

negative electrode

A

cathode

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10
Q

Metals that are usually solid

A

Neutral Metals

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11
Q

Metals that dissolve in water

A

DISSOCIATED METALS

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12
Q

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

A

POLARIZATION

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13
Q

2 Forms of Polarization

A
  1. Concentration polarization
  2. Activation polarization/Hydrogen polarization/Cathodic Polarization
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14
Q

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

A

Concentration Polarization

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15
Q

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

A

decreases

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16
Q

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

A

ACTIVATION/HYDROGEN/CATHODIC POLARIZATION

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17
Q

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

A

decrease

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18
Q

In corrosion processes, ______ usually has the greater effect.

A

activation polarization

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19
Q

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

A

gold, platinum, palladium, metal

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20
Q

Metals in combined form are called as ___

A

MINERALS

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21
Q

Combined forms
OCCSS

A
  1. Oxides
  2. Carbonates
  3. Chlorides
  4. Sulfides
  5. Sulfates
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22
Q

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

A

Corrosion

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23
Q

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

A

Corrosion

24
Q

Loss of useful properties due to corrosion

A

*weakening of metallic material

*metal becomes brittle (lesser malleable, lesser ductile)

*decaying of surface

25
Q

Types of metal corrosion

A
  1. Dry or Chemical Corrosion
  2. Wet or Electrochemical Corrosion
26
Q

Oxidation of metal by oxygen or by other gases

A

Dry or Chemical Corrosion

27
Q

Oxidation of metal exposed to an aqueous environment

A

Wet or Electrochemical Corrosion

28
Q

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

A

wet corrosion

29
Q

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

A
  1. Dissolve into solution
  2. Combine with available anions or water to form IONIC COMPOUNDS/HYDRATED OXIDES
30
Q

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

A

negative, higher

31
Q

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

A

GENERAL CORROSION

32
Q

2 required conditions for Gen. Corrosion to occur

A
  1. Metal is exposed to a moisture/aqueous environment.
  2. Chemical reaction bet. metal and aqueous solution to form an oxide
33
Q

compound containing oxygen

A

OXIDE

34
Q

Water is an _____

A

ampholyte

35
Q

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

A

AMPHOLYTE

36
Q

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

A

Impurities, imperfections

37
Q

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

A

GENERAL OVERALL CORROSION

38
Q

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

A

Iron (II) Oxide or FERROUS OXIDE (FeO)

39
Q

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

A

Iron (III) Oxide or Ferric Oxide (Fe2O3)

HEMATITE

40
Q

plus 3 oxidation state

A

FERRIC IRON (Fe3+)

41
Q

plus 2 oxidation state

A

FERROUS IRON (Fe2+)

42
Q

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

A

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

MAGNETITE

43
Q

metal does not become active in the corrosion reaction

A

PASSIVITY

44
Q

most desirable oxide layer, adheres best on the metal

A

FE3O4

45
Q

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

A

ZIRCONIUM, CHROMIUM, ALUMINUM, STAINLESS STEEL

46
Q

Factors affecting General Corrosion Rate

A
  1. Temperature
  2. Water velocity
  3. Oxygen
  4. pH
  5. Metal surface condition and composition
  6. Dissolved solids
47
Q

Substances (like O2) that remove the adsorbed atomic hydrogen

A

DEPOLARIZERS

48
Q

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

A

pH < 4.0

49
Q

Corrosion rate is relatively independent of pH of the solution

A

pH 4 - 10

50
Q

corrosion rate is observed to fall as pH is INCREASED

A

pH > 10

51
Q

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

A

pH < 4.0

52
Q

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

A

pH bet. 4 and 12

53
Q

@ high temp, corrosion rate increases

A

pH beyond 12

54
Q

Plant pH to prevent corrosion

A

pH 9 and 11

55
Q

another factor affecting General corrosion rate

A

exposure TIME of metals to corrosive environment

Alawi_CHEMISTRY (5 decks)

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