UNIT4 Spectroscopy (edit!)

Question 1

What is spectroscopy?

Answer 1

Interactions of readiation and matter

Question 2

How is spectroscopic analysis measured?

Answer 2

Amount of radiatio produced or absorbed

Question 3

What waves are used?

Answer 3

γ-ray, X-ray, ultraviolet (UV), visible, infrared (IR), microwave, and radio-frequency (RF)
ALSO acoustic, massm electron spectroscopy

Question 4

What is the most widely used method?

Answer 4

elucidation of molecular structure and quantitative and qualitative determination

Question 5

What is electromagnetic radiation?

Answer 5

Wave with properties of a wavelength, frequency, velocity and amplitude

Question 6

What medium of transport does electromagnetic radiation use?

Answer 6

No medium

Question 7

How can electromagnetic radiation be seen?

Answer 7

discrete packets of energy paticles —> photons or quanta

Question 8

What is the energy of the photon?

Answer 8

Proportional to its frequency

Question 9

How is electromagnetic radiation modeled?

Answer 9

Waves consisting of perpendicularly oscillating electric and magnetic feild

Question 10

Amplitude

Answer 10

Strength at a maximum in a wave

Question 11

Period (p)

Answer 11

time in seconds for successive maxima and minima to pass a point in space

Question 12

Frequency v

Answer 12

number of oscillations that occur in one second –> 1/p

Question 13

What is the unit of frequency?

Answer 13

Hertz (Hz)

One cycle per second

Question 14

What is the wavelength?

Answer 14

Linear distance between sucessive maxima or minima

Question 15

Velocity

Answer 15

speed that depends on the medium and frequency

Question 16

Is the frequency or velocity constant?

Answer 16

Frequency

Question 17

What is wave number

Answer 17

Way to describe electromagntic radiation –> number of waves per centimeter = 1/λ

Question 18

What is a photon?

Answer 18

Particle of electromagnetic radiation having zero mass and an energy of hv

Question 19

What is the equation for wavenumber?

Answer 19

E=hv=hc/λ=hcv~

Question 20

What is plank’s constant?

Answer 20

6.63*10^-34J

Question 21

What are the most important interactions in spectroscopy

Answer 21

transitions between different E levels

Question 22

Visible light spectrum

Answer 22

380-780

Question 23

What is visible spectrum

Answer 23

180-380nm

Question 24

What is another word to spectrochemical methods?

Answer 24

OPtical methods, even when you cannot see some of them

Question 25

How do you begin a spectroscopic method?

Answer 25

Sample is stimulated by applying energy (heat, electirc, light, particles

Question 26

What is the state of the analyte before the stimulus?

Answer 26

Lowest- energy / ground state

Question 27

Why is the analyte in the ground state?

Answer 27

In order to transition to a higher more excited state

Question 28

How do we acquire information about the analyte?

Answer 28

Measure the electromagnetic readiation emitted or the amount of electromagnetic readiation absorbed

Question 29

The results of spectroscopy is expressed by...

Answer 29

Graphically by a spectrum --> plot of emitted/absorbed radiation as a function of frequency, wavelength or wavenumber

Question 30

Emission spectroscopy?

Answer 30

Methods which the stimulus is heat or electrical

Question 31

Chemiluminescence spectroscopy?

Answer 31

Excitation of analyte by chemical reaction

Question 32

Absorption spectroscopy

Answer 32

light absorbed as a function of wavelength

Question 33

photoluminesence spectroscopy

Answer 33

emission of photon measured following absorption

Question 34

What are the most important forms of photoluminescence?

Answer 34

Fluorensence and phosphorescence

Question 35

Every molecule is able of absorbing....

Answer 35

its own characteristic frequencies of elec radiation

Question 36

What is the process of absorption of radiation?

Answer 36

Transfer energy to the molecule and results in a decrease in intensity of incident

Question 37

What happens to the beam in absorption of radiation?

Answer 37

Attenuates the beam in accordance to the Beer-Lambert Law

Question 38

What is Beer's Law

Answer 38

Amount of attenuation depends on the concentration of absorbing moleules and the path length

Question 39

According to Beer's Law, the longer the length of the medium?

Answer 39

The greater attenuation

Question 40

According to Beer's Law, the higher the concentration of absorbers

Answer 40

The stronger the attenuation

Question 41

What is the transmittance

Answer 41

the fraction of incident radiation transmitted by the solution T=P/P0

Question 42

Absorbance as a solution is denoted as

Answer 42

A=-logT=-log%T+log100=2-log%t

Question 43

What happens with radiation at the cell wall

Answer 43

Reflection and scattering losses | --> can be substantial

Question 44

How do we compensate for the scattering losses?

Answer 44

Reagent blank

Question 45

What is absorbance according to Beer's Law?

Answer 45

Absorbance is directly proportional t the concentration of the absorbing species c and to the path length c A=Ebc E--> absorptivity in L mol^-1 cm^-1

Question 46

Why are high molar absorptivities good?

Answer 46

high analytical sensitivity

Question 47

The longer the path length, the _____ the attenuation

Answer 47

Greater

Question 48

As absorbance increases, transmittance ____

Answer 48

decreases

Question 49

The study of the interaction between electromagnetic radiation and matter is...

Answer 49

Spectroscopy

Question 50

Electromagnetic radiation is modeled as a ____ to explain different phenomena such as reflection, refraction, interference and diffraction

Answer 50

wave

Question 51

When an excited chemical molecule returns to its ground state it ___ energy

Answer 51

emits

Question 52

A plot of the emitted or absorbed radiation as a function of frequency, wavelength or wavenumber is ____

Answer 52

Spectrum

Question 53

Beer's law relates the __ of the electromagnetic beam to the path length and the concentration of absorbing species

Answer 53

attenuation

Question 54

True or false: the attenuation of the electromagnetic beam results only from molecules absorbing electromagnetic energy

Answer 54

False

Question 55

Vibration of chemical bounds is induced by ___

Answer 55

Infrared light

Question 56

True or false: IR radiation causes transitions in the electronic, vibrational and rotational states.

Answer 56

False. Only in the rotational and vibrational states

Question 57

Total energy in atomic and molecular absorption is a sum of what energies?

Answer 57

electronic, vibrational and rotational

Question 58

What do the spectra of liquid, gas, nonpolar and polar states look like?

Answer 58

gas: many peaks resulting from transitions liquid & non polar solvents: no fine structure, plus still peaks polar solvents: band becomes blurred

Question 59

Why do polar solvent have a blurred spectrum?

Answer 59

Because collisions between particles tend to spread energies of quantum states and the spectrum appears as a single broad peak

Question 60

Beer's law only applies to what type of solutions?

Answer 60

Dilute

Question 61

Name some instrumental deviations to Beer's law?

Answer 61

- Measurements must be made with monochromatic source radiation - Polychromatic sources must be used with a filter to isolate band - Stray radiation/light: result of scattering and reflection - mismatched cells (intercept k will appear in calibration curve)

Question 62

Name a chemical deviation to Beer's Law

Answer 62

Absorbing species dissociates, associates or reacts with solvent to give a product that absorbs differently