Exam III Flashcards

1
Q

Cu->cu2+ and 2e-

A

Oxidation

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2
Q

2(AG+ + e-)-> 2 AG

A

Reduction

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3
Q

Reduction

A

Gain of electrons

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4
Q

Oxidation

A

Loss of electrons

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5
Q

Cathode

A

Where reduction happens

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6
Q

Anode

A

Where oxidation occurs

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7
Q

dG=-nFE

A

N-number of transferred
F-96500 c/mol
E- potential

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8
Q

Standard reduction potential

A

Ecell=Eright-Eleft

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9
Q

Potentiometry

A

measure potential and relate to concentration by nernst equation

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10
Q

Potentiometry

A

measure potential and relate to concentration by nernst equation
ref electrode II soln I indicator electrode

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11
Q

Reference electrodes

A

Calomel-Hg I Hg2Cl2, KCl II
E=0.2444
Silver silver chloride electrode- Ag I AgCl, KCl II
E=0.199

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12
Q

Membrane electrodes

A

glass electrodes
liquid membrane electrodes
crystalline membrane electrodes
gas sensing probes

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13
Q

glass electrodes

A

ref electrode II external analyte soln I glass membrane I internal ref soln of known [], Cl-, AgCl I Ag
charge difference creates potential across membrane
H+, Li+, Na+, Nh4+

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14
Q

liquid membrane electrode

A

like glass but polymeric ion exchange; Ca2+, Cl-, NO3-, ClO4-, K+

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15
Q

crystalline membrane electrode

A

solid crystalline materials; Br-, Cd2+, Cl-, Cu2+, CN-, F-, I-, Pb2+, Ag+, S2-, SCN-

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16
Q

gas sensing probes

A

detect change in pH due to dissolved gas; CO2, NO2, H2S, SO2, HF, HCN, NH3

17
Q

Coulometry

A

measure charge necessary to completely to completely reduce sample

18
Q

Voltametry

A

control potential, measure current

3 electrode cell- working and counter in electrolysis circuit and working and reference in reference circuit

19
Q

working/counter electrodes

A

Pt, Au, glassy carbon, pyrolytic graphite

Dropping mercury electrode (DME)

20
Q

problems with electrode detecting analyte

A

diffusion-analyte must break barrier

migration due to electric field, and convection

21
Q

linear scan voltammetry application

A

dissolved O2 sensors

glucose sensors

22
Q

Differential Pulse Polarography (DPP)

A

+: resolution (.04-.05 mV)
mixtures
-: sensitivity (10E-7-10E-8 M DL)

23
Q

Stripping methods

A

can be used to determine mix of metals
analyte must be able to deposit out as solid
DL=10E-6-10E-9

24
Q

DPP and stripping methods

A

must have relatively clean sample

eliminate diffusion problems

25
Q

Atomic Spectroscopy

A

quantifies atomic species-ions or atoms, not molecules
line spectra
absorbance, emission, fluorescence

26
Q

Atomic Spectroscopy Instrumentation

A

Source, atomixer, monochromator, detector, read out

27
Q

Atomic Spec source

A

hollow cathode tubes specific for a metal

28
Q

Atomic Spec monochromator

A

grating

29
Q

Atomic Spec Detector

A

PMTs-detect 1 element at a time

DAD/CCD- allow multiple elements at a time

30
Q

Atomic Spec Atomizers

A

Flame

electrothermal/graphite furnace

31
Q

flame atomizer

A

aspirates soln into flame, evaporating
absorbance, emission
cheap and easy
least sensitive (ppm)

32
Q

electrothermal/graphite furnace

A

heat tube to volatilize sample
absorbance, fluorescence
medium cost, medium ease of use
medium sensitivity (10-100ppm)

33
Q

Inductively coupled plasma (ICP)

A
emission
MS
multielement analysis
most expensive, hardest to use
high sensitivity (ppb-ppt)
34
Q

Flame instrument

A

source, chopper, reference and sample cells, monochromator, detector, read out

35
Q

Ion chromatography

A

uses HPLC instrumentation (solvent res., pump, sample injector, column, detector, readout)
column- stationary phase is charged
detector-conductivity detector
DL in ppm
+: ion analyses, multielement, low cost
-: not very low DL, requires analyte in soln

36
Q

X-ray Fluorescence

A

absorb xray proton, ionize e- out of atom, creates hole in core e-
wavelength and energy dispersive
no soln required
problems with matrix effects
DL: .01-100%mass
+: nondestructive, no sample prep, portable
-: difficulty in calibration, relatively high DL

37
Q

Laser induced breakdown spectroscopy

A

laser to sample creates plasma, heat excites metals, emits light which is transferred fiber optically to monochromator, and PMT detector
+: no sample prep, nondestructive, spatial resolution 1-100um, portable
-: matrix effects cause hard to calibrate, precision 5-10%, DL: 1-100ppm