L10 - spectroscopy

Question 1

what is spectroscopy

Answer 1

the use of electromagnetic radiation to characterise matter

Question 2

what is resonance

Answer 2

match frequency of the motion of an atom with electromagnetic radiation

Question 3

absorbance and transmission spectroscopy

Answer 3

absorption of radiation opposite of transmission

Question 4

what are chromophores

Answer 4

conjugated molecules that absorb light

Question 5

beer Lambert law

Answer 5

absorbance = ε l c
ε = molar absorptivity
l = path length (cm)
c = concentration

Question 6

how does infrared spectroscopy work

Answer 6

uses longer wavelengths and lower frequencies than UV-Vis spectroscopy; the resonance frequencies are associated with bond vibrations: stretching, bending and twisting.

Question 7

why is H20 stretch frequency broader than C02

Answer 7

H20 is liquid and hydrogen bond interactions interfere with the frequency

Question 8

infrared spec cons

Answer 8

not good for complex, macromolecules

Question 9

what is fluorescence spectroscopy

Answer 9

light source creates an excitation beam with passes through sample cuvette

detector is placed 90° from excitation beam

Question 10

what is quantum yield

Answer 10

efficiency of the return on excitation energy

Question 11

what is stokes shift

Answer 11

difference in peak excitation wavelength and emission wavelength.

Question 12

fluorescence spectroscopy pros

Answer 12

sensitive (single molecule detection and analysis)

Question 13

cons of NMR

Answer 13

insensitive (need high concentrations)