Exam 3

Front 1

Atomic spectroscopy must provide background correction to

Back 1

distinguish analyte signal from absorption, emission, and optical scattering of the sample matrix, the flame, plasma, or white-hot graphite furnace.

Front 2

The Boltzmann distribution describes

Back 2

the relative populations of different states at thermal equilibrium.

Front 3

The general types of atomic spectroscopy are

Back 3

absorption, fluorescence, and emission

Front 4

Hollow cathode lamps

Back 4

are used for atomic absorption (flame and furnace) only

Front 5

For a given element, the atomization method that can detect the lowest concentration is

Back 5

furnace

Front 6

Compared to a flame, a graphite furnace

Back 6

requires less sample.

Front 7

In atomic emission spectroscopy, it is desirable to have a high concentration of the element in the form of

Back 7

atoms in the excited state.

Front 8

The common source for infrared spectroscopy is

Back 8

globar

Front 9

Resolution of two closely spaced wavelengths depends on the

Back 9

width of the exit slit.

Front 10

red to a dispersive spectrometer, a diode array spectrometer

Back 10

is faster.

Front 11

double-beam spectrophotometer

Back 11

Light alternatively passes through the sample and reference, directed by a rotating mirror, chopper

Front 12

photomultiplier tube is

Back 12

a very sensitive device in which electrons emitted from the photosensitive surface strike a second surface called a dynode, which is positive with respect to the photosensitive emitter.

Front 13

A deuterium arc lamp is commonly used as a source for

Back 13

Ultraviolet

Front 14

the correct order for the parts in the schematic of a general scanning spectrophotometer?

Back 14

Light source, wavelength selector, sample compartment, light detector, and read-out device

Front 15

Spectrophotometric analysis based on Beer's Law

Back 15

requires the use of monochromatic light.

Front 16

Electromagnetic radiation in the range from 200 to 800 nm causes

Back 16

electronic, vibrational and rotational excitation.

Front 17

A molecule which has absorbed a photon of energy in the visible range could move from the excited electronic state S1 to a highly excited vibrational level of the ground state (S0) with the same energy. This process is

Back 17

internal conversion

Front 18

Absorbance is proportional to

Back 18

concentration.

Front 19

Coulometric titrations are a

Back 19

constant-current method.

Front 20

Coulometry is a form of chemical analysis based on

Back 20

counting the electrons used in a reaction.

Front 21

A fluoride ion-selective electrode is used in two solutions. Both solutions have [F-] of 5.00 x 10-3 M, but one has a pH of 2.00 and the other a pH of 7.00. You would expect that

Back 21

the potential would be higher in the pH 2.00 solution.

Front 22

A S.H.E. is a reference electrode, Pt can used as a metallic indicator electrode, and sodium concentration can be determined with an ion-selective electrode

Back 22

true

Front 23

A galvanic cell(also called a voltaic cell) uses

Back 23

a spontaneouschemical reaction to generate electricity

Front 24

a salt bridge is

Back 24

a U-shaped tube filled with a gelcontaining a high concentration of KNO3(or other electrolyte that does not affect the cell reaction).

Front 25

When Q< 1 and thus [reactant] > [product],

Back 25

ln Q< 0, so Ecell> Eocell.

Front 26

When Q= 1 and thus [reactant] = [product],

Back 26

ln Q= 0, so Ecell= Eocell.

Front 27

When Q>1 and thus [reactant] < [product], ln Q> 0,

Back 27

so Ecell< Eocell.

Front 28

SHE

Back 28

Arbitrarily assigned a value of 0 V

Front 29

AG/AgCl

Back 29

-0.197 V

Front 30

SCE

Back 30

-0.241 V

Front 31

Ideally, the voltage changes by

Back 31

59.16 mV (at 25°C) for each factor-of-10 change in [Ag+].

Front 32

in ISE, It can be shown that the potential difference across the membrane

Back 32

depends only on the activity of analyte in the outer solution

Front 33

With glass electrodes: Because [Cl−] is fixed in each compartment and because [H+] is fixed on the inside of the glass membrane, the only variable is the

Back 33

pH of analyte solution outside the glass membrane.

Front 34

Ion-selective electrodes are the method of choice for 4 of the chem 7 test:

Back 34

Na+, K+, Cl−, pH, and PCO2.

Front 35

The smaller the selectivity coefficient,

Back 35

the less the interference by X.

Front 36

Disadvantages
of ISE

Back 36

Precision is rarely better than 1%, and usually it is worse. Electrodes can be fouled by proteins or other organic solutes, which lead to sluggish, drifting response. Certain ions interfere with or poison particular electrodes. Some electrodesare fragile and have limited shelf life.Electrodesrespond to the activityof uncomplexed analyte ion. Therefore, ligands must be absent or masked.

Front 37

Advantages of ISE

Back 37

Ion-selective electrodesrespond linearly to the logarithmof analyteactivity over four to six orders of magnitude. Electrodesdo not consume unknowns, and they introduce negligible contamination. Response time is secondsor minutes, so electrodesare used to monitor flow streams in industrial applications. Color and turbidity do not hinder electrodes. Microelectrodes can be used inside living cells

Front 38

current is positive if reduction occurs at

Back 38

the working electrode

Front 39

In general, then, when the applied voltage is constant, the cathode potential

Back 39

drifts to more negative values and solutes more easily reduced than H+will be electrolyzed.

Front 40

Single beam absorption spectrometer components:

Back 40

light source, wavelength selector, sample, light detector

Front 41

The part of a molecule responsible for light
absorptionis called a

Back 41

chromophore.

Front 42

Luminescenceis inherently more or less sensitive than absorption?

Back 42

more

Front 43

The formation constantfor the antibody-antigen complex is

Back 43

very large, whereas the binding of the antibody to other molecules is weak

Front 44

Aptamers

Back 44

are ∼15–40-base-long pieces of DNA (deoxyribonucleic acid) or RNA (ribonucleic acid) that strongly and selectively bind to a specific molecule.

Front 45

tungsten source emits

Back 45

ir

Front 46

dueterium source emits

Back 46

uv

Front 47

A Globar is a silicon carbiderod that emits

Back 47

Infrared

Front 48

Fully constructive interference occurs

Back 48

when the difference in length of the two paths is an integral multiple of the wavelengthof light.