Experiment # 9: Optical Method of Analysis Use of Beer’s Law on a KMn04
Gregorio, Justin Edrik A.
March 2013
Department of Chemical Engineering, Faculty of Engineering
University of Santo Tomas
España, Manila

Abstract The purpose of this analytical laboratory experiment is to determine the unknown concentration of potassium permanganate (KMnO4) solution by finding its absorbance through the use of spectrophotometer. The preparation of four known concentration of KMnO4 was done namely, 2.00×10-4M, 1.50×10-4M, 1.00×10-4M, 5.00×10-5M, respectively and is to be place on the spectrophotometer with the unknown and distilled water for the determination of each concentration’s absorbance. As the concentration is proportional with the absorbance …show more content…

As a result, has the units: L·mol-1·cm-1. The path length is measured in centimeters. Because a standard spectrometer uses a cuvette that is 1 cm in width, is always assumed to equal 1 cm. Since absorption, , and path length are known, we can calculate the concentration of the sample. III. Methodology

a. Materials and Equipment * Standard KMnO4 solution * Spectrophotometer * Flasks * 250mL volumetric flask * Distilled H2O * Wash Bottle * Cuvettes * Pipette * Rubber Aspirator b. Procedure
For the preparation of the aliquot of standard KMnO4 solution, we carefully measured a 2.53mL of standard KMnO4 (0.01975M) using a pipette and diluted it to the mark in a 250mL volumetric flask. After preparing the aliquot, we prepared four flasks containing 10mL, 30mL, 10mL and another 10mL of the solution respectively. We then diluted each with distilled water with 0mL, 10mL, 10mL, and 30mL respectively.
Each portion of each solution was transferred on different clean cuvettes and was placed on the carousel respectively. The zero (first one) in the carousel has the cuvette with distilled water and the last one has the unknown. We then used the spectrophotometer to find the wavelength in lambda max (ƛmax) and the instrument was then calibrated.
The absorbance of the solutions was measured covering the wavelength range from 440nm