ANACHEM 11 12 Flashcards

1
Q

relationship between chemical reaction
and electricity (movement of electrons

A

ELECTROCHEMISTRY

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2
Q

it is the measurement of current/voltage
generated by the activity of an ion

A

ELECTROCHEMISTRY

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3
Q

Electrochemistry Analysis

A
  • redox titration
  • potentiometry - widely used
  • amperometry
  • polarography
  • electrogravimetry
  • voltammetry
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4
Q
  • A pair of
    electrodes in contact with an electrolyte
    solution
A

Electrochemical Cell

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5
Q

An
electrochemical cell which
spontaneously produces current (or
energy) when the electrodes are
connected externally by a
conducting wire.

A

. Galvanic or Voltaic Cell -

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6
Q

An electrochemical cell through
which current is forced by a battery
or some other external source of
energy. (such as battery, DC,
alternate current)

A

Electrolysis or Electrolytic Cell

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7
Q

The
algebraic sum of the individual electrode
potentials of an electrochemical cell at
zero current

A

Theoretical Cell Potential -

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8
Q
  • the amount of
    potential that is lost on the way from the
    reference electrode to the working
    electrodes.
A

Ohmic Drop, IR

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9
Q

A potential
developed across a boundary between
electrolytes differing in concentration or
chemical composition

A

Liquid-junction Potential

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10
Q

one way of measuring how
easily the substance loses on
electron.

A

Standard Electrode Potential

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11
Q

Electrode potential
measured in solutions where all
reactants and products are at
unit activity.

A

Standard Electrode Potential

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12
Q

The potential
of an electrode measured relative to a
standard, usually the SHE. It is a
measure of the driving force of the
electrode reaction and is temperature
and activity dependent

A

Electrode Potential E

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13
Q

This consists of a platinum electrode
coated with platinum black to catalyze
the electrode reaction and over the
surface of which hydrogen at 760 mm of
mercury is passed.

A

Standard Hydrogen Electrode

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14
Q

One in which the halfcell reactions are reversed by reversing
the current flow; such a cell is said to be
in thermodynamic equilibrium

A

REVERSIBLE CELL

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15
Q

The electrode at which
reduction occurs

A

CATHODE

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16
Q

The electrode at which
oxidation occurs.

A

ANODE

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17
Q

occur together but opposite
direction.

A

Half-cell Reactions

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17
Q

The additional
potential required to cause some
electrode reactions to proceed at an
appreciable rate

A

Activation Overpotential

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18
Q

Oxidation or reduction reaction
occurring at an electrode

A

Half-cell Reactions

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19
Q

In an oxidation/reduction reaction
electrons are transferred from one
reactant to another. (occurs together)

A

REDOX REACTIONS

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20
Q

consists of two conductors called
electrodes, each of which is
immersed in an electrolyte solution.

A

Electrochemical Cells

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20
Q
  • the
    additional voltage that is needed to carry
    out electrolysis in addition to the
    standard cell potential.
A

Concentration Overpotential

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21
Q

In most of the cells that will be of
interest to us, the solutions
surrounding the two electrodes are
different and must be separated to
avoid direct reaction between the
reactants

A

Electrochemical Cells

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22
Q

consume
electricity. In contrast to a voltaic cell,
requires an external source of
electrical energy for operation.

A

electrolytic cells

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22
Q

store electrical
energy.

A

Galvanic cells

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23
Q

: In redox
methods an indicator electrode is used
to sense the presence or change in
concentration of the oxidized and
reduced forms of a redox couple.

A

INDICATOR ELECTRODE

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24
Q

an
electrode that has a stable and well known electrode potential.

A

REFERENCE ELECTRODE

25
Q

The electrode
consists of two concentric glass tubes,
the inner one of which contains
mercury in contact with a paste of
mercury, mercury (1) chloride
(calomel), and potassium chloride.

A

Calomel Electrode

26
Q

This consists of a silver wire, coated
with silver chloride and in contact with
a solution of potassium chloride
saturated with silver chloride

A

Silver-silver Chloride Electrode

26
Q

Used to find the concentration of
solute in a solution

A

Potentiometry

27
Q

Potential is measured under the
conditions of no current flow

A

Potentiometry

28
Q

based on measuring the potential of
electrochemical cells without drawing
appreciable current.

A

Potentiometry

29
Q
  • w sample
    dilution;
A

INDIRECT ISE

29
Q

an electrochemical
transducer capable of
responding to one given ion.
they are selective and sensitive
method; but not specific

A

ion-selective
electrodes.

30
Q
  • w/o sample
    dilution;
A

DIRECT ISE

31
Q

a potential that
varies in the
concentration of analyte

A

Indicator
Electrode

32
Q

Potentiometry USES

A

pH and pCO₂ tests

33
Q

an accurately
known electrode
potential

A

Reference
Electrode

34
Q

ideal reference electrode has a
potential that is accurately known.
constant, and completely insensitive to
the composition of the analyte
solution

A

Reference
Electrode

34
Q

half-cell having a known electrode
potential that remains constant at
constant temperature and is
independent of the composition of the
analyte solutioN

A

Reference
Electrode

35
Q

Reference
Electrode Some common examples

A

a. Saturated calomel electrode
b. Silver/silver hydrogen electrode
c. Standard hydrogen electrode
d. pH electrode

35
Q

has a potential that varies in a known
way with variations in the
concentration of an analyte.

A

INDICATOR ELECTRODE

35
Q

ideal indicator electrode responds
rapidly and reproducibly to changes in
the concentration of an analyte ion

A

INDICATOR ELECTRODE

36
Q

INDICATOR ELECTRODE TYPES

A
  1. metallic,
  2. membrane, and
  3. ion-sensitive field effect
    transistors
37
Q

One
potential advantage of an ion-selective
electrode is the ability to incorporate it
into a flow cell for the continuous
monitoring of wastewater streams.

A

➢ Environmental Chemistry

37
Q

ion-selective
electrodes are important sensors for
clinical samples because of their
selectivity for analytes in complex
matrices

A

Clinical Chemistry.

38
Q

Use a pH
electrode to monitor the change in pH
during the titration for determining the
equivalence point of an acid-base
titration.

A

Potentiometric Titrations.

39
Q

the
known pH of a reference solution is
determined by using two electrodes,
a glass electrode and a reference
electrode, and measuring the voltage
(difference in potential) generated
between the two electrodes

A

glass-electrode method,

39
Q

thin membrane is called the

A

Electrode membrane.

40
Q

liquid inside the glass electrode
usually has a pH o

A

7

40
Q

immersed
in a solution of unknown pH

A

glass electrode (indicator)
and SCE (reference)

41
Q

This other electrode, paired with the
glass electrode, is called the

A

reference electrode

42
Q

measurements
provide a rapid and convenient
method for determining the activity of
a variety of cations and anions

A

Direct Potentiometry

42
Q

e technique requires only a
comparison of the potential developed
in a cell containing the indicator
electrode in the analyte solution with
its potential when immersed in one or
more standard solutions of known
analyte concentration

A

Direct Potentiometry

43
Q

serve as the internal reference for the
glass electrode.

A

n indicator glass
electrode and a silver/silver
chloride reference —

44
Q

measurements
are also readily adapted to applications
requiring req continuous and
automatic recording of analytical data

A

Direct Potentiometry

44
Q

endorsed by the National Institute of
Standards and Technology (NIST),
similar organizations is based upon
potentiometric determination of pH of
unknown solution followed after
calibration of the meter with standard
buffers

A

operational definition of pH

45
Q

remarkably versatile tool for the
measurement of pH under many
conditions

A

glass/calomel electrode system

45
Q

Values registered by
the glass electrode tend to be
somewhat high when the pH is less
than about 0.5

A

The Acid Error

46
Q

ordinary glass
electrode tends to be somewhat
sensitive to alkali metal ions and gives
low readings at pH values greater than
9.

A

the Alkaline Error.( sodium error)

47
Q

operational definition of pH is
endorsed

A

National Institute of
Standards and Technology (NIST)
and the IUPAC

48
Q

may cause
erratic electrode performance.

A

Dehydration

49
Q

has been found that
significant errors may occur when the
pH of samples of low ionic strength,
such as lake or stream water, is
measured with a glass/calomel
electrode system

A

Errors in Low Ionic Strength
Solutions.

50
Q

A
fundamental source of uncertainty for
which a correction cannot be applied is
the junction-potential variation
resulting from differences in the
composition of the standard and the
unknown solution

A

Variation In Junction Potential

51
Q

provide data
that are more reliable than data from
titrations that use chemical indicators
and are particularly useful with colored
or turbid solutions and for detecting
the presence of unsuspected species.

A

Potentiometric Titrations

51
Q

inaccuracies in the
preparation of the buffer used for
calibration or any changes in its
composition during storage cause an
error in subsequent pH measurements

A

Error in the pH Of The Standard
Buffer

52
Q

offer
additional advantages over direct
potentiometry. Because the
measurement is based in the titrant
volume that causes a rapid change in
potential near the equivalence point,

A

Potentiometric titrations