Spectroscopic and Optical Methods

Question 1

Define spectroscopy

Answer 1

absorption or emission spectrum

Question 2

Define spectrophotometry

Answer 2

quantitative measurement of the absorption or emission

Question 3

UV-Vis

Answer 3

Ultraviolet-Visible Spectrophotometry

Question 4

FT-IR

Answer 4

Fourier-transform infrared sprectrophotometry

Question 5

FAAS

Answer 5

Flame atomic absoption spectrophotometry

Question 6

Refractometry

Answer 6

bending of light through media

Question 6

Polarimetry

Answer 6

polarization (plane rotation) of light; for optically active compounds

Question 7

Turbidimetry

Answer 7

scattering of light

Question 8

Colorimetry

Answer 8

measurement of color variation

Question 9

Common range of wavelength in UV-Vis

Answer 9

200 nm to 700 nm

Question 10

Arrange in increasing wavelength

Answer 10

: Gamma, x, UV, visible, microwave, radio waves (FM, AM, long)

Question 11

Main parts of spectrophotometer

Answer 11

Light source, monochromator, sample compartment, detector

Question 12

Light source for UV and Visible

Answer 12

deuterium lamp for UV, tungsten lamp and gallium LED for visible

Question 13

Sample compartment for UV and Visible

Answer 13

Quarts for UV, regular glass or polystyrene for visible

Question 14

Subparts of monochromator

Answer 14

: entrance slit, dispersion device, exit slit

Question 15

What is Beer-Lamber Law?

Answer 15

Relates concentration to absorbance: A = kbC = -log I/I0

Question 16

T/F: Color absorbed is complementary to the color transmitted or reflected

Answer 16

: True

Question 17

Concentration can be calculated from calibration curve if the ___ is known

Answer 17

absorbance

Question 18

Calibration curve axes

Answer 18

y-axis: absorbance, x-axis: concentration

Question 19

Calibration curve axes

Answer 19

y-axis: absorbance, x-axis: concentration

Question 20

Calibration curve trend

Answer 20

Linear

Question 21

Measurement must be made in the ___ for Beer’s law to apply

Answer 21

maximum absorption wavelength

Question 22

Radiation must be ___ for Beer’s Law to apply

Answer 22

monochromatic

Question 23

Analyte must be ___ and ___ before and after absorption for Beer’s Law to apply

Answer 23

stable and chemically same

Question 24

____ solutions must be used since non-linearity is observed if not

Answer 24

Dilute

Question 25

An instrumental error that can lead to multiple wavelengths

Answer 25

polychromatic radiation

Question 26

An instrumental error that occurs when light is not from the source

Answer 26

stray light

Question 27

An instrumental error that can cause scattering and reflection

Answer 27

cuvette imperfection

Question 28

What chemical deviation can occur during spectrophotometry

Answer 28

degradation or change in analyte chemical structure

Question 29

Formula of refractive index

Answer 29

n = speed of light, c/velocity of light in medium, v

Question 30

Refractive index determines the ___ in medium

Answer 30

refraction of light

Question 31

Refractive index of air

Answer 31

n = 1

Question 32

Refractive index of water

Answer 32

n = 1.333

Question 33

Refractive index of diamond

Answer 33

n = 2.42

Question 34

Snell’s Law

Answer 34

n1 sin theta 1 = n2 sin theta 2

Question 35

Snell’s Law

Answer 35

n1 sin theta 1 = n2 sin theta 2

Question 36

Snell’s Law

Answer 36

n1 sin theta 1 = n2 sin theta 2

Question 36

Molar refraction formula

Answer 36

A = (M n^2 – 1)/(density n^2 + +2)

Question 37

Molar refraction of a binary mixture is the ____ and ____ of the pure components

Answer 37

sum of product of mole fraction and molar refractions

Question 38

Molar refraction is an ___ property

Answer 38

additive

Question 39

Molar refraction does not vary much with _____, but it is a strong function of _____

Answer 39

temperature; concentration

Question 40

Measurement of refractive index

Answer 40

Abbe refractometer and hand-held refractometer

Question 41

Electric and magnetic fields travelling perpendicularly across direction of propagation

Answer 41

Electromagnetic wave

Question 42

Fields (either the electric field or the magnetic field) are propagating in random orientation

Answer 42

Unpolarized light

Question 43

Some organic compounds (such as sugars) can ___ polarized light

Answer 43

rotate

Question 44

Specific rotation at temeperature and wavelength formula

Answer 44

Specific rotation = (optical rotation) / (path length) (concentration)

Question 45

Optical rotation and concentration relationship

Answer 45

directly proportional

Question 46

Optical rotation and concentration relationship

Answer 46

directly proportional

Question 47

Applications of spectroscopic and optical methods

Answer 47

characterization, determination of concentration

Question 48

If maximum absorbance wavelength is > ___; ____ the sample

Answer 48

1.5; dilute

Question 49

Blot refractometer prism with ___ and not paper or tissue

Answer 49

Kimwipe

Question 50

Adjust ____ using upper knob of refractometer; shadow must be sharp

Answer 50

dispersion

Question 51

Adjust ____ using lower knob; shadow must ____

Answer 51

refraction; fall on intersection crossed line

Question 52

levo-rotations: _____ dextro-rotations: _____

Answer 52

counterclockwise (left); clockwise (right)

Question 53

T/F: Higher alcohol-water concentration, higher refractive index

Answer 53

True

Question 54

refractive index of water ____ refractive index of alcohol

Answer 54

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