Objective

To estimate the amount of solute dissolved in a saturated solution of 4-chlorobenzaldehyde in chloroform, by UV spectroscopy.

Procedure

Known concentrations of 4-chlorobenzaldehyde is made-up in chloroform. A UV spectrum of a further diluted solution is obtained to determine the λmax (wavelength of maximum absorbance) of the solution, using which absorbance of solutions of different concentrations is obtained. The solutions are made by diluting the previously prepared solution. From the absorbance values, the molar extinction coefficient (molar absorptivity) ε, is calculated using Beer's law A = εcl, by determining the slope of a plot of absorbance Vs concentration. Once the molar absorptivity is obtained the absorbance and thereby concentration of the saturated solution is determined. This is done by obtaining the absorbance of dilute solutions (known dilution) of the saturated solution.

Results


Discussion


Conclusion

Experiment aborted because one of the values of the dilute solutions, has been mis-calculated.

Log


2008-10-29

15:00 Made-up two solutions, 211A and 211B of 4-chlorobenzaldehyde in chloroform by weighing 7.05mg (5.015mM) and 7.12mg (5.056mM) 4-chlorobenzaldehyde respectively in 5mL chloroform in a volumetric flask.

2008-10-30

10:40 Prepared a saturated solution of 4-chlorobenzaldehyde by vortexing it in chloroform for 30s. More solute was added four times until no more of it would dissolve. After the last addition, vortex time was increased to 1.5min.
12:30 Started obtaining a UV-Vis scan for a solution...this was done by performing serial dilutions until the intensity of absorbance was with-in the detectable limits (below 3 units)..The dilutions thus performed are listed in the spreadsheet Exp211-WS1.