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Instrumental Analysis > Test 1 > Flashcards

Test 1 Flashcards

1
Q

Spectroscopy

A

use of E/M energy, particles, or sound to study matter

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2
Q

Qualitative

A

What is present?

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3
Q

Quantitative

A

How much is present?

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4
Q

Limitations in using human eye

A
  1. Need standards for each unknown studied. 2. Uncolored solutions. 3. Variations in light source. 4. Variations in eye sensitivity. (color blindness)
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5
Q

All Instruments have:

A

source, monochromator, sample, detector, readout device

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6
Q

Types of Errors

A
  1. Random 2. Systematic
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7
Q

Random

A

(Indeterminate) Noise Example: Random variations in mass of a weighing boat.

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8
Q

Systematic

A

(Determinate) Instrumental bias, personal, method Example: Always dispensing total volume of a pipette even though pipette marked TD.

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9
Q

Absolute Error

A

E(abs)=X-Xt Xt accepted or true value and X is the measurement or average of several measurements.

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10
Q

Relative Error

A

E(relative)=(X-Xt)/Xt

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11
Q

Population

A

All measurements of an observable. Infiinite. (impossible to get)

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12
Q

Sample

A

A subset of all the possible measurements. Finite. (Your results)

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13
Q

Samples mean

A

Summation of all samples divided by number of samples.

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14
Q

Sample Std. Dev

A

Sx=sqrt(Summation of (xi-xmean)^2/(N-1))

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15
Q

Signal (S)

A

A voltage or current produced by the spectrometer in response to a change in the absorption or emission of photons by a sample. (Avg. peak height above avg. baseline)

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16
Q

Noise(N)

A

Extraneous and unwanted signals that are superimposed on the desired signal. N=max. std. dev of baseline.

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17
Q

SNR

A

Signal to Noise Ratio. Measure of quality of a signal in spectrum.

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18
Q

Spectra are…

A

variations in a voltage as wavelength is scanned.

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19
Q

Time…

A

elapses as a spectrum is scanned

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20
Q

Signal & Noise…

A

can be thought of variations in a voltage w/ respect to time or in terms of their frequency

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21
Q

Don’t confuse the frequency…

A

of a signal and noise with the frequency of the light being absorbed or emitted in the spectroscopy.

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22
Q

S/N need to observe a signal…

A

depends on frequency of noise and if some knowledge of the signal exists.

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23
Q

Types of Noise:

A
  1. Chemical 2. Instrumental 3. Thermal of Johnson 4. Shot 5. Flicker 6. Environmental
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24
Q

Chemical Noise

A

Noise arising from uncontrollable variables that affect chemistry of system being analyzed.

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25
Q

Instrumental Noise

A

Noise associated with components of instrument.

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26
Q

Shot Noise

A

Occurs whenever electrons are transferred across electrical junctions.

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27
Q

Thermal of Johnson Noise

A

Noise that contains all frequencies and arises from thermal motion of electrons in resistive elements of electric circuits.

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28
Q

Flicker Noise.

A

Noise whose frequency spectrum is inversely proportional to frequency, the cause of which is not well understood.

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29
Q

Environmental Noise

A

Noise from surrounding environment

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30
Q

S/N improvement

A

=sqrt(number of spectra averaged)

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31
Q

Uncertainty in adding or subtracting

A

=sqrt(Summation(uncertainty squared))

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32
Q

Uncertainty in multiplying or dividing (x=p*q/r)

A

Sx/x=sqrt(summmation((uncertainty/value)squared))

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33
Q

Uncertainty in exponential x=p^y

A

Sx/x=y*Sp/P

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34
Q

Uncertainty in logarithm x=ln(p)

A

Sx=Sp/P

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35
Q

TV

A

Total volume of, not in, glassware

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36
Q

SD

A

Smallest division of glassware

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37
Q

Method of least squares

A

A mathematical technique that draws the best line through data by minimizing the residuals.

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38
Q

If you blank…

A

(0,0) should be a data pt.

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39
Q

E/M Radiation

A

Beam of sub-atomic particles called photons that possess an oscillating electric and magnetic field

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40
Q

Frequency

A

(curly v) number of oscillations of the field per second. (Hz)

41
Q

Period

A

(P) time between 2 successive maxima (s)

42
Q

Wavelength

A

(lamba) distance between successive maxima (nm)

43
Q

Velocity

A

(vi) rate at which a wavefront moves through a medium i. (m/s)

44
Q

Wave number

A

(sigma) number of waves or oscillations per cm. (/cm)

45
Q

Power

A

(P) energy that reaches an area per second (Watt)

46
Q

Intensity

A

(I) Power per unit solid angle (Watts/steradian)

47
Q

10-180 nm

A

Vacuum UV

48
Q

180-400 nm

A

UV

49
Q

400-700 nm

A

Visible

50
Q

2.5-15 micron

A

InfraRed

51
Q

.3-10 m

A

Nuclear Magnetic Resonance

52
Q

Vacuum UV

A

10-180 nm

53
Q

UV

A

180-400 nm

54
Q

Visible

A

400-700 nm

55
Q

InfraRed

A

2.5-15 micron

56
Q

Nuclear Magnetic Resonance

A

.3-10 m

57
Q

When two or more waves….

A

traverse the same space the resultant field at any time is the sum of the fields of individual waves

58
Q

Wave equation

A

Y=A*sin(2pi*frequency*time+phase angle)

59
Q

Destructive interference

A

phase angle differs by +/- pi A=A1-A2

60
Q

Constructive interference

A

equal phase angles, A=A1+A2

61
Q

Plane Polarized

A

All electric fields of a beam of photons lie in one plane

62
Q

Monochromatic

A

All photons have same frequency

63
Q

Coherent

A

All photons have same frequency and phase angle

64
Q

Energy

A

of a single photon is dependent of it’s frequency E=hv

65
Q

Velocity

A

v=frequency*wavelength Vvac=c=3*10^8 m/s

66
Q

Velocity is always slower…

A

in a medium

67
Q

frequency is always…

A

constant from one medium to another

68
Q

Refractive index

A

ni measure of interaction of medium i with E/M Radiation

69
Q

ni=

A

c/vi=wavelength vacuum/wavelength

70
Q

Refractive index….

A

is usually wavelength dependent and reported at a wavelength

71
Q

Refraction

A

change in direction of beam of E/M radiation on passing from one medium into another with different refraction index. sin(theta1)/sin(theta2)=refraction index1/refraction index2=v1/v2=wavelength1/wavelength2

72
Q

Reflection

A

angle of incidence equals angle of reflection

73
Q

Intensity of reflection

A

Ireflected/Iincident=(n2-n1)^2/(n1+n2)^2

74
Q

Diffraction

A

process in which beam of parallel waves of radiation is bent as it passes by a sharp barrier or through narrow opening

75
Q

Diffraction equation

A

CF=BCsin(theta) DE=OD*sin(theta) n*wavelength=BCsin(theta)=BC8DE/OD constructive when n=0(equal path length) or n=1 (path length differ by one wavelength)

76
Q

Absorption

A

removal of select frequency from a beam of radiation as it passes through a medium

77
Q

Types of Absorption

A

Electronic, vibrational, and magnetic

78
Q

Electronic Absorptio

A

H(1s)+hv->H(2s) Uv, Vis

79
Q

Vibrational absorption

A

HCl+hv-> IR

80
Q

Magnetic Radiation

A

H(^) +hv-> ESR, NMR

81
Q

Photons are produced…

A

When excited molecules and atoms return to lower energy levels

82
Q

Absorbance equation

A

A=log(Pincident/Ptransmitted)=Molarabsorptivity*pathlength*concentration

83
Q

Emission

A

Fluorescence power=constant*concentration

84
Q

Thermal Radiation

A

Radiation emitted from a solid when heated to incandescence

85
Q

Difference between absorption setup and fluorescence

A

both source-wavelength selector-sample-detector-readout, but fluorescence has additional wavelength selector after sample

86
Q

Discontinuous Spectrum

A

Tall narrow peaks (think sodium spectra)

87
Q

Continuous Source Spectrum

A

Think SWCNTs ROlling peaks

88
Q

Effective bandwidth

A

full width of emission peak at half its height

89
Q

H2 or D2 light source

A

continuous light source, electrical excitation of H2 or D2 at low pressure UV 160-375 nm

90
Q

Tungsten Filament

A

Electrically heated W filament (320-2500) Vis-IR

91
Q

Halogen Lampe

A

W lamp with Halogen gas that minimizes W deposition on glass

92
Q

Xenon Arc lamp

A

electrical discharge in Xe 250-600 UV-Vis

93
Q

Nernst Glower

A

electrically heated rare earth oxides, ZrO2 and Y2O3 320-20000 nm Vis-IR

94
Q

LED

A

incoherent semiconductor that emits narrow band of light when electrically biased in forward direction 420-720 Vis 10 x’s more efficient than W in Vis blue peak ~450, phosphorescence peak ~550

95
Q

Metal Vapor Lamp

A

Gaseous metal atoms at low P excited with electrical discharge

96
Q

Hollow Cathode Lamp

A

excited metal atoms fro a sepecial geometry cathode (AA spectroscop)

97
Q

Laser

A

light amplification by stimulated emission of radiation coherent light source inverted population needed for laser to operate

98
Q

Absorption Filter

A

Colored glass which absorbas a select band of light and transmits others. Bandwidth ~ 40 nm

99
Q

Interference Filter

A

transparent dielectric filter sandwiched between two partially reflective surfaces. Constructive and destructive interference causes selective transmittance. Bandwidth ~5 nm. m*wavelength=2*T ^^T is thickness of dielectric ^^wavelength dielectric*ndielectric=wavelength vacuum

Instrumental Analysis (1 decks)

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