Exam III

Question 1

Cu->cu2+ and 2e-

Answer 1

Oxidation

Question 2

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

Answer 2

Reduction

Question 3

Reduction

Answer 3

Gain of electrons

Question 4

Oxidation

Answer 4

Loss of electrons

Question 5

Cathode

Answer 5

Where reduction happens

Question 6

Anode

Answer 6

Where oxidation occurs

Question 7

dG=-nFE

Answer 7

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

Question 8

Standard reduction potential

Answer 8

Ecell=Eright-Eleft

Question 9

Potentiometry

Answer 9

measure potential and relate to concentration by nernst equation

Question 10

Potentiometry

Answer 10

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

Question 11

Reference electrodes

Answer 11

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

Question 12

Membrane electrodes

Answer 12

glass electrodes
liquid membrane electrodes
crystalline membrane electrodes
gas sensing probes

Question 13

glass electrodes

Answer 13

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+

Question 14

liquid membrane electrode

Answer 14

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

Question 15

crystalline membrane electrode

Answer 15

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

Question 16

gas sensing probes

Answer 16

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

Question 17

Coulometry

Answer 17

measure charge necessary to completely to completely reduce sample

Question 18

Voltametry

Answer 18

control potential, measure current

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

Question 19

working/counter electrodes

Answer 19

Pt, Au, glassy carbon, pyrolytic graphite

Dropping mercury electrode (DME)

Question 20

problems with electrode detecting analyte

Answer 20

diffusion-analyte must break barrier

migration due to electric field, and convection

Question 21

linear scan voltammetry application

Answer 21

dissolved O2 sensors

glucose sensors

Question 22

Differential Pulse Polarography (DPP)

Answer 22

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

Question 23

Stripping methods

Answer 23

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

Question 24

DPP and stripping methods

Answer 24

must have relatively clean sample

eliminate diffusion problems

Question 25

Atomic Spectroscopy

Answer 25

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

Question 26

Atomic Spectroscopy Instrumentation

Answer 26

Source, atomixer, monochromator, detector, read out

Question 27

Atomic Spec source

Answer 27

hollow cathode tubes specific for a metal

Question 28

Atomic Spec monochromator

Answer 28

grating

Question 29

Atomic Spec Detector

Answer 29

PMTs-detect 1 element at a time | DAD/CCD- allow multiple elements at a time

Question 30

Atomic Spec Atomizers

Answer 30

Flame | electrothermal/graphite furnace

Question 31

flame atomizer

Answer 31

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

Question 32

electrothermal/graphite furnace

Answer 32

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

Question 33

Inductively coupled plasma (ICP)

Answer 33

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

Question 34

Flame instrument

Answer 34

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

Question 35

Ion chromatography

Answer 35

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

Question 36

X-ray Fluorescence

Answer 36

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

Question 37

Laser induced breakdown spectroscopy

Answer 37

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