CEE 772

Fall 2005

Homework #1

Based on Lab #1: UV/Vis Spectrophotometry

a. Objective:

Determine molar absorptivity of 2,4 Dintrophenol (including uncertainty).

b. Procedure:

Prepare the following solutions by diluting the stock 10 mM solutions (prepared by Gladys)

• 1 mM
• 0.5 mM
• 0.2 mM
• 0.1 mM
• 0.05 mM
• 0.02 mM

Measure absorbance of each at a wavelength of 254 nm, and for the dinitrophenol only measure the absorbance at 360 nm too.

Proposed Assignments:

Spectrophotometer	Location	Group
Lambda 3A	308	Mercer, Sahu
ThermoSpectronic Genesys 10 UV	304 or 213	Briggs, Lui
Hach DR/4000U	304	Huang, Heymann
Spec 21D	Marston 24
Spec 20 Genesys	Marston 24
Spectronic 20 (standard)	308	Islam, Goodwell

c. Report

Prepare on brief technical report per group (2 in a group) including the following elements

• Graphical and tabular absorbance vs concentration data for each spectrophotometer
• Assessment of molar absorptivity based on those data
• Assessment of uncertainty in that number
• Comparison of the estimated molar absorptivity with any published values
• What if any role does pH play in this exercise?

Assigned: 14 Sept 2005

Due: 21 Sept 2005