Instrumental Analysis-Chapter 6

Front 1

Define Wavenumber and give the related symbol.

Back 1

v (v with bar on top)
reciprocal of wavelength in cm.
v(bar v) = 1 / lambda

Front 2

Define frequency and give the symbol for frequency.

Back 2

The number of oscillations of the field that occur per second. Symbol = v

Front 3

Define wavelength and give the symbol for wavelength.

Back 3

Symbol = lambda
The linear distance between any two equivalent points on successive waves

Front 4

What is the equation that relates wavelength and frequency?

Back 4

C = lambda x v

Front 5

What is the value for the speed of light in a vacuum?

Back 5

c = 3.00 x 10^8 m/s

Front 6

What doe sthe Fourier transform help us to do with complex waves?

Back 6

Any periodic function, regardless of complexity, can be described by a sum of simple sine or cosine terms.

Front 7

Does radiation travel more slowly through a transparent substance than a vacuum? If so, why?

Back 7

The rate at which radiation is propagated through a transparent substance is less than its velocity in a vacuum. Why? Radiation interacts with the matter.

Front 8

Describe the polarization of atoms during the transmission of radiation.

Back 8

Light energy deforms e- clouds, the energy required for polarization is only momentarily retained (10^-14 to 10^-15), and reemitted without alteration, but the light is slowed.

Front 9

What is the refractive index of a material?

Back 9

A measure of a transmission medium's interaction with radiation.

Front 10

Describe the impact of wavelength on the intensity of scattered radiaiton.

Back 10

A very small fraction of the radiation transmitted is transmitted away from the original path.

Front 11

Describe the impact of particles size on the intensity of scattered radiaiton.

Back 11

The intensity of scattered radiation increases with particle size. Shorter wavelength are scattered more intensely.

Front 12

Define Raleigh scattering and give an example.

Back 12

Scattering by molecules or aggregates of molecules with dimensions significantly smaller than the wavelength of the radiation. Sunlight is scattered by air molecules to produce a blue background.

Front 13

What is the Tyndall effect? Give an example of the Tyndall effect.

Back 13

Tyndall effect-scattering is sufficiently intense to be seen by the naked eye (example: High powered laser shone through a campfire).

Front 14

Write the equation that relates voltage and radiant power during spectrochemical measurement and state what each symbol stands for.

Back 14

S = kP
S = a voltage
P = radiant power

Front 15

Define dark current. Write the equation that relates dark current, radiant power, and signal.

Back 15

Most real detectors exhibit a small constant response even in the absence of light. S = kP + kd(d should be below k)

Front 16

Define power and write the symbol for power.

Back 16

The energy of the beam that reaches a given area per second. Symbol = P

Front 17

Write the equation for transmittance and state what each symbol stands for.

Back 17

T = P/Po (o below P)
P = power of the beam after passing through the sample.
Po = power of the beam before passing through the sample.

Front 18

Write the equation that relates absorbance to transmittance

Back 18

A = -logT

Front 19

Write the equation that relates absorbance and concentration and state what each symbol stands for including measurement units

Back 19

A = ebc (e should be symbol for molar absorbtivity, (Beer's Law)
b = pathlength (cm)
c = conc. (M)
e = molar absorbtivity (L/(cm)(mole)

Front 20

Define the Ground state of a molecule.

Back 20

The ground state of an atom is the lowest energy state for that atom.

Front 21

Define electronic excitation.

Back 21

The process by which electrons in a substance are promoted from their ground state orbitals to higher electronic orbitals by absorption of energy.

Front 22

Define blackbody radiation.

Back 22

Also called the continuum spectrum: light profile for solids that are heated to incandescence. Spectrum depends on temperature. Good light sources.

Front 23

Name three sources of energy that could be used to excite electrons in a substance.

Back 23

Electronic, Vibrational, Rotational

Front 24

What did Maxwell Planck say about possible states that atoms ions and molecules can exist in?

Back 24

That they can only exist in discrete states.

Front 25

What happens to a bond in a molecule if more energy is applied to the molecule than is need to promote the molecule to its highest energy state?

Back 25

bonds break. The highest energy state is just before the bond breaks.

Front 26

Define Emission of radiation.

Back 26

Produced when excited particles relax to lower energy levels (a photon is emitted)

Front 27

Define Electronic Transistion

Back 27

Movement of an electron from one energy state to another

Front 28

Define Absorption

Back 28

The removal of a portion of a light beam traveling through matter due to atoms interacting with photons

Front 29

Define Non-radiative relaxation

Back 29

excited molecule or atom has its energy converted to kinetic energy.

Front 30

What is the name for the type of spectrum that is produced when a solid is heated to incandescence?

Back 30

Continuum spectrum

Front 31

(T/F) during absorption of radiation atoms and molecules in the sample are promoted from an excited state to the ground state

Back 31

False: promotes the particles from the ground state to the excited state.

Front 32

Which of the following would you expect to have a band spectrum?
- Atoms
- Molecules

Back 32

- band spectrum (molecular absorption)- characteristic absorbance profile for molecules in the liquid or solid state

Front 33

Molecules have more complex absorption spectra than atoms because the energy state of the molecule depends on the overlap of what three energy categories for the molecule?

Back 33

E(electronic) + E(vibrational) + E(rotational) = E