Transcript Chapter 13 & 14

Chapter 13 & 14
CHM 411
Spring 2013
Suroviec
I. UV-Vis molecular absorption
I. Beers Law
Deviations and limitations
to Beers Law:
Example
• A solution containing 5.24 mg/100 mL of A
(MW 335 g/mol) has a transmittance of 55.2%
in a 1.50 cm cell at 425 nm. Calculate the
molar absorptivity of A at this wavelength.
Example
• A simultaneous determination for cobalt and
nickel gives the following information:
Molar Absorptivity
365 nm
700 nm
Co
3529
428.9
Ni
3228
10.2
Absorbance (1.00 cm cell) 365 nm
700 nm
Unknown
0.026
0.426
• Calculate the molar concentration of nickel
and cobalt.
II. Types of Instruments
1. Single Beam
2. Multichannel
III. Applications
A. Absorbing species
• Electronic transitions:
Absorption of UV-VIS
radiation is excitation
of bonding electrons
p, s and nonbonding
B. Types of transitions
B. Types of transitions