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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
Advantages and Disadvantages of Flame
Advantages: - fast, easy to use - inexpensive - high precision Disadvantages: - large sample quantities needed - limited to alkali and some earth metals - issues with refractory elements
26
Electrical Domains
A. Analog B. Time C. Digital
27
Instrument
Converts characteristic of an analyte into information that can be interpreted
28
Basic Instrument Design
Stimulus (energy source) —> System under study —> Response
29
Transducer
Converts data from one domain to an electrical domain
30
Types of Blanks:
*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.
31
External Standard
Chemicals prepared separately from the standard
32
Internal Standard
Substance added in a constant amount to all samples, blanks, and calibration standards
33
What does the GC mass spec do?
detects mass to charge ratio; shows isotopes
34
About the atomic absorbable:
- linear plot obtain due to demonstration of beers law
35
If data obtained from the AA is NOT linear:
1. You could obtain more points. | 2. You have maxed out the detector; dilute your samples
36
Where are vibrational states found?
Between energy levels
37
What does atomic X-ray do?
Sees what elements exist within a sample.
38
What is the most widely used technique?
AA; atomic absorbance
39
What is the AA used for?
- when looking for a metal and trying to determine concentration - used in pharmaceutical manufacturing - it is cheap, fast, and reliable
40
What is the atomic fluorescence used for?
Environmental applications | - lower detection limit than AA
41
What is X-ray fluorescence used for?
Rocks and minerals, steel/cement industry
42
Steps in Flame Atomization:
1. Nebulization 2. Desolvation 3. Volatilization 4. Dissociation 5. Ionization
43
Desolvation
Removal of a solvent
44
Nebulization
bulk liquid divided into drops
45
Doppler Effect
- 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
Photomultiplier
Changes photon to electron; converting it allows it to be able to be detected by computer.
47
Band gap
Difference in energy required to move an electron between bands; difference between HOMO and LUMO
48
HOMO
highest occupied molecular orbital
49
LUMO
Lowest unoccupied molecular orbital
50
Factors of band gaps:
A. Size B. Shape C. Make-up (content)
51
Conductor
Electrons flow thru conduction band with out an issue
52
Semiconductor
Band gap distance can be jumped; but requires some form of energy
53
Elergy across a band gap can.....
Absorb or emit radiation (color)
54
LOOK AT QUANTUM NUMBERS
DO IT BITCH
55
Quantum Numbers:
- n - l - ml - ms
56
n
gives the shell | - ex) Na = 3, Cl=3, He =1
57
l
subshells (s,p,d,f) - values of zero to one - s (l=0) - p (l=1) - d (l=2) - f (l=3)
58
When selecting an instrument consider.....
``` A. Bias B. Precision C. Sensitivity D. Detection Limit E. Dynamic Range F. Selectivity ```
59
Boxcar Averaging
Method of noise reduction; assumes signal varies slowly with time; average of a small number of points
60
Precision
Degree of mutual agreement of data obtained
61
Bias
Measure of systematic error
62
Sensitivity
Instruments ability to discriminate between small difference in analyte concentration.
63
Detection Limit
Minimum concentration of analyte that can be detected | *signal to noise ratio = 3:1*
64
Signal to Noise Ratio
3 to 1
65
Dynamic Range
Range of concentrations at which quantitative measurements can be obtained; distance between LOQ and LOL
66
LOQ
Limit of quantitative measurement
67
LOL
Limit of linear response
68
Selectivity
Degree to which method is free from interference by other species contained in the sample
69
Noise
Background picked up by an instrument | *always present; can be reduced.
70
Types of Noise:
A. Instrumental | B. Chemical
71
Chemical Noise
Caused by uncontrollable variables that affect the chemistry of the system being analyzed; ex. Fluctuations in temperature, pressure, humidity, light, lab fumes, etc.
72
Types of Instrumental Noise:
A. Flicker Noise B. Shot Noise C. Thermal (Johnson) Noise D. Environmental Noise
73
Thermal (Johnson) Noise
Caused by thermal agitation of electrons
74
Shot Noise
Found whenever an electron crosses a junction
75
Flicker Noise
Sources not totally understood; inversely proportional to frequency (1/f)
76
Environmental Noise
Observed in different forms that originate from your surroundings; ex. Elevator, ratio, can be anything
77
Noise Reduction
``` 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
Raman Scatterings
Scattering of light where wavelength is changed
79
Mie Scatterings
- Scattering of molecules that are larger than the wavelength - ex. Why the clouds are white
80
Rayleigh Scattering
- Scattering of molecules that are smaller than the wavelength of radiation - ex. Why the sky is blue
81
Scattering
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
Reflection
Occurs when light cross an interface between media that differ in refraction index. Ex. Puddle in middle of road; mirage
83
Spectroscopy
Study of interaction of electromagnetic radiation (light) and matter.
84
Volatilization
Process where a dissolved sample is vaporized
85
Dissociation
The splitting of a molecules into smaller molecules or atoms
86
Ionization
Process by which an atom or molecules obtains a positive/negative charge due to the loss/gain of electrons
87
Quant Number ml
``` 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
Quantum Number ms
Spin on electron

Instrumental Chemistry (5 decks)

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