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Instrumental Chemistry > Exam 1 > Flashcards

Exam 1 Flashcards

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1
Q

Piezoelectric Effect

A

The ability of certain materials to generate an electric charge in response to an applied mechanical stress

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2
Q

Refractive Index

A

Ratio of velocity of light to its velocity traveling thru an object/medium

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3
Q

Lock-in Amplifier

A

Noise reduction; recombines reference beam and sample beam after a sample has been split

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4
Q

Transmission

A

Light traveling through an object

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5
Q

Velocity of light is lower when…..

A

Traveling thru something

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6
Q

Wave Propagation

A

Travel/movement of waves

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7
Q

Types of Interferences

A
  1. Constructive: increases amplitude

2. Destructive: decreases amplitude; can eliminate a wave completely at its max

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8
Q

Magnetron

A

Vacuum tube generates microwaves using the interaction between a string of electrons and a magnetic field, moving past a series of open metal cavities

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9
Q

Know the structure of a wave

A
  • crest
  • trough
  • wavelength
  • wave height
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10
Q

Types of Waves

A

Shortest wavelength = gamma

Longest wavelength = radio

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11
Q

Wave Trends

A

A. As wavelength decreases, energy increases.
B. The shorter the wavelength, the more power within a wave packet.
C. The more power within a wave packet, the greater the interaction between light and matter.

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12
Q

Electromagnetic radiation can be viewed as…..

A

A. Wave

B. Particle

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13
Q

Spectroscopy

A

The study of the interaction between electromagnetic radiation and matter.

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14
Q

Fourier transformation

A

Noise reduction; converts a time domain to a frequency domain

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15
Q

Calibration

A

Determines relationship between analytical response and analyte concentration

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16
Q

Ensemble Averaging

A

Data sets are averaged point by point with similar data

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17
Q

Direct Comparison

A

Sample that is directly compared to a primary standard; ex. Titration

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18
Q

Multivariate Calibration

A

Using multiple instrument responses to analyze an analyte

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19
Q

Matrix Affects

A

Interactions within a sample that can cause extra species in the mixture that are not found in the blank; can cause blanks to become worthless

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20
Q

Difference between a singlet and a triplet state:

A

A. In an excited singlet state; the electron has the same spin orientation as it had in the ground state (one arrow down, one arrow up)
B. In an excited triplet state; the promoted electron has the same spin orientation as the other electron (both arrows up)

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21
Q

When are singlet and triplet state formed?

A

When an electron is excited to a higher energy level.

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22
Q

Forbidden State

A

Spectral line associated with absorption or emission of light by an atom, which undergoes a transition that is not allowed by a transition rule.

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23
Q

The Stokes Shift

A

Difference between positions of the absorption and emission spectra of the same electron transition; occurs when relaxation to a lower energy excited state takes place prior to emission.

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24
Q

Advantages and Disadvantages of Inductively Coupled Plasma

A

Advantages:

  • high limit of detection
  • low chemical interference
  • stable, reproducible signal

Disadvantages:

  • high maintenance and operating costs
  • samples must be dissolved in solution
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25
Q

Advantages and Disadvantages of Flame

A

Advantages:

  • fast, easy to use
  • inexpensive
  • high precision

Disadvantages:

  • large sample quantities needed
  • limited to alkali and some earth metals
  • issues with refractory elements
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26
Q

Electrical Domains

A

A. Analog
B. Time
C. Digital

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27
Q

Instrument

A

Converts characteristic of an analyte into information that can be interpreted

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28
Q

Basic Instrument Design

A

Stimulus (energy source) —> System under study —> Response

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29
Q

Transducer

A

Converts data from one domain to an electrical domain

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30
Q

Types of Blanks:

A

used to calibrate instruments
A. Ideal - identical to sample but withOUT analyte.
B. Solvent - contains the same solvent as the sample.
C. Reagent - contains solvent AND all reagents used in the sample preparation.

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31
Q

External Standard

A

Chemicals prepared separately from the standard

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32
Q

Internal Standard

A

Substance added in a constant amount to all samples, blanks, and calibration standards

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33
Q

What does the GC mass spec do?

A

detects mass to charge ratio; shows isotopes

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34
Q

About the atomic absorbable:

A
  • linear plot obtain due to demonstration of beers law
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35
Q

If data obtained from the AA is NOT linear:

A
  1. You could obtain more points.

2. You have maxed out the detector; dilute your samples

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36
Q

Where are vibrational states found?

A

Between energy levels

37
Q

What does atomic X-ray do?

A

Sees what elements exist within a sample.

38
Q

What is the most widely used technique?

A

AA; atomic absorbance

39
Q

What is the AA used for?

A
  • when looking for a metal and trying to determine concentration
  • used in pharmaceutical manufacturing
  • it is cheap, fast, and reliable
40
Q

What is the atomic fluorescence used for?

A

Environmental applications

- lower detection limit than AA

41
Q

What is X-ray fluorescence used for?

A

Rocks and minerals, steel/cement industry

42
Q

Steps in Flame Atomization:

A
  1. Nebulization
  2. Desolvation
  3. Volatilization
  4. Dissociation
  5. Ionization
43
Q

Desolvation

A

Removal of a solvent

44
Q

Nebulization

A

bulk liquid divided into drops

45
Q

Doppler Effect

A
  • an increase or decrease in the frequency of sound/light/etc. as the source and observer move towards or away from each other
  • if it’s pointing towards you, you see the blue shift (wavelengths are at a higher energy)
  • if it’s pointing away from you, you see red shift (wavelengths are at a lower energy)
46
Q

Photomultiplier

A

Changes photon to electron; converting it allows it to be able to be detected by computer.

47
Q

Band gap

A

Difference in energy required to move an electron between bands; difference between HOMO and LUMO

48
Q

HOMO

A

highest occupied molecular orbital

49
Q

LUMO

A

Lowest unoccupied molecular orbital

50
Q

Factors of band gaps:

A

A. Size
B. Shape
C. Make-up (content)

51
Q

Conductor

A

Electrons flow thru conduction band with out an issue

52
Q

Semiconductor

A

Band gap distance can be jumped; but requires some form of energy

53
Q

Elergy across a band gap can…..

A

Absorb or emit radiation (color)

54
Q

LOOK AT QUANTUM NUMBERS

A

DO IT BITCH

55
Q

Quantum Numbers:

A
  • n
  • l
  • ml
  • ms
56
Q

n

A

gives the shell

- ex) Na = 3, Cl=3, He =1

57
Q

l

A

subshells (s,p,d,f)

  • values of zero to one
  • s (l=0)
  • p (l=1)
  • d (l=2)
  • f (l=3)
58
Q

When selecting an instrument consider…..

A 
A. Bias
B. Precision
C. Sensitivity
D. Detection Limit
E. Dynamic Range
F. Selectivity
59
Q

Boxcar Averaging

A

Method of noise reduction; assumes signal varies slowly with time; average of a small number of points

60
Q

Precision

A

Degree of mutual agreement of data obtained

61
Q

Bias

A

Measure of systematic error

62
Q

Sensitivity

A

Instruments ability to discriminate between small difference in analyte concentration.

63
Q

Detection Limit

A

Minimum concentration of analyte that can be detected

signal to noise ratio = 3:1

64
Q

Signal to Noise Ratio

A

3 to 1

65
Q

Dynamic Range

A

Range of concentrations at which quantitative measurements can be obtained; distance between LOQ and LOL

66
Q

LOQ

A

Limit of quantitative measurement

67
Q

LOL

A

Limit of linear response

68
Q

Selectivity

A

Degree to which method is free from interference by other species contained in the sample

69
Q

Noise

A

Background picked up by an instrument

*always present; can be reduced.

70
Q

Types of Noise:

A

A. Instrumental

B. Chemical

71
Q

Chemical Noise

A

Caused by uncontrollable variables that affect the chemistry of the system being analyzed; ex. Fluctuations in temperature, pressure, humidity, light, lab fumes, etc.

72
Q

Types of Instrumental Noise:

A

A. Flicker Noise
B. Shot Noise
C. Thermal (Johnson) Noise
D. Environmental Noise

73
Q

Thermal (Johnson) Noise

A

Caused by thermal agitation of electrons

74
Q

Shot Noise

A

Found whenever an electron crosses a junction

75
Q

Flicker Noise

A

Sources not totally understood; inversely proportional to frequency (1/f)

76
Q

Environmental Noise

A

Observed in different forms that originate from your surroundings; ex. Elevator, ratio, can be anything

77
Q

Noise Reduction

A 
A. Instrumental design
B. Grounding & shielding
C. Amplifiers
D. Analog filtering
E. Modulation
F. Synchronous demodulation
G. Lock-in amplifier
H. Software methods (ensemble averaging, boxcar averaging, Fourier transformation)
78
Q

Raman Scatterings

A

Scattering of light where wavelength is changed

79
Q

Mie Scatterings

A
  • Scattering of molecules that are larger than the wavelength
  • ex. Why the clouds are white
80
Q

Rayleigh Scattering

A
  • Scattering of molecules that are smaller than the wavelength of radiation
  • ex. Why the sky is blue
81
Q

Scattering

A

Change in the direction of a vector; small portion of incident light hits destructive interfaces and light is transmitted at all angles from original path.

82
Q

Reflection

A

Occurs when light cross an interface between media that differ in refraction index.
Ex. Puddle in middle of road; mirage

83
Q

Spectroscopy

A

Study of interaction of electromagnetic radiation (light) and matter.

84
Q

Volatilization

A

Process where a dissolved sample is vaporized

85
Q

Dissociation

A

The splitting of a molecules into smaller molecules or atoms

86
Q

Ionization

A

Process by which an atom or molecules obtains a positive/negative charge due to the loss/gain of electrons

87
Q

Quant Number ml

A 
Indicates the energy shift; position in sub shell where electron resides.
S (1 spot)
P (3 spots)
D (5 spots)
F (7 spots)
Negative to positive
88
Q

Quantum Number ms

A

Spin on electron

Instrumental Chemistry (5 decks)

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