L2 Rich: ir spectroscopy part 1

Question 1

what does IR stand for?

Answer 1

infrared spectroscopy

Question 2

what is shot through a sample?

Answer 2

IR radiation

Question 3

what do molecules absorb and what does this promote?

Answer 3

absorbs certain frequencies which leads to a higher vibrational energy level

Question 4

Historically IR spectra are shown as ______

Answer 4

transmission

Question 5

Spectra can be plotted as _________

Answer 5

absorption

Question 6

what can IR spectroscopy be preformed on?

Answer 6

Solids, Liquids and Gases

Question 7

what type of techniques an be used on solids?

Answer 7

• KBr disc
• Nujol mull
• Attenuated Total Reflection (ATR)

Question 8

what type of IR be done on liquids?

Answer 8

• Salt plates

* Attenuated Total Reflection (ATR)

Question 9

what type of IR be done on gases ?

Answer 9

gas cell

Question 10

how does sample preparation for KBr disc work?

Answer 10

solid sample ground with dry KBr
placed in mould and compressed
KBR shows cold flow and forms transparent disc

Question 11

what are some issues with KBr?

Answer 11

fragile and difficult

sample recovery difficult

Question 12

does KBr absorb IR?

Answer 12

no

Question 13

how does sample preparation for Nujol mull work?

Answer 13

• sample ground and dispersed in mineral oil
• mixed
  thin layer spread between polish sodium chloride plates

Question 14

How many absorption bands does Nujol have?

Answer 14

3 major bands

Question 15

Possible to run in _______________ as a supplement

Answer 15

hexachlorobutadiene

Question 16

How is sample recovery with the Nujol Mull preparation?

Answer 16

difficult

Question 17

whats used to analyse liquids?

Answer 17

two dismountable IR windows

Question 18

what does qualitative analysis of liquids involve?

Answer 18

a drop of sample compressed between two NaCl or KBr discs without spacers to create a film

Question 19

can salt plates be used for aqueous samples?

Answer 19

no

Question 20

Quantitative analysis uses cells with?

Answer 20

a variable or fixed path length

Question 21

Absorbances for gases can be weak, this means what is needed?

Answer 21

a long pathlength is often needed

Question 22

what is needed for IR on gas cell?

Answer 22

• Glass gas cell with non IR absorbing windows at each end
• Single crystals of NaCl, KBr, CaF2 or even CsI cut shape and polished
• Possible to also use balloons and gas sampling bags

Question 23

why is low pressure needed when finding IR of gas cells?

Answer 23

to avoid interactions

Question 24

start back at

Answer 24

ATR