IR spectroscopy Flashcards
(20 cards)
Relationship between frequency and wavelength
Inverse proportionality
Relationship between wave numbers and frequency
Direct proportionality
What is the unit for wave numbers
cm-1
What is a wave number
1÷ wave length in cm, a greater unit that wavelength
What type of energy can covalent bonds absorb
IR rad.
What does absorbing IR cause bonds to do
Vibrate MORE
What is the speed of vibration based on 2
Mass of molecule and strength of bond
2 types of vibration and describe
Sretch: bond extends or compresses
Bend: bond angle changes
What type of radiation will each bond absorb
Radiation of the same frequency as it’s natural freq
Wave number range of IR
200-4000cm-1
What is analysed to produce an IR spectrum
The emerging beam
What needs to be stated when identifying an absorbance peak 3
The bond
The FG
The wavenumber range
‘broad’ for the O-H bond in carboxylic acid
X and Y axis labels of a IR spectra
X= wave number cm-1
Y= Transmittance %
Finger print region?
<1500cm-1, unique to molecules of the same structure so can be compared to known molecules in a database to identify
Use of IR spectra 2
Monitor local air pollution from NO, MO, CO and hydrocarbons
IR based breathalyser to measure ethanol in captured breath
what is the more reliable bond to analyse in breathalyser and why
C-O rather that O-H bc oh can be found in water vapour in breath
Explain global warming
Visible light and IR emitted from the sun pass into atmosphere and warm earth surface
Some energy is re emitted but as IR
Bonds in CO2, CH4, H2O absorb IR and vibrate more
Bonds re emit energy increasing temp of atmosphere
Causing global warming
Why is the greenhouse effect necessary
To keep enough warmth to sustain life on earth
Examples of renewable enegy
Wind, solar, hydroelectric geothermal
3 most abundant greenhouse gasses
CO2, CH4, H2O
