Question

To varify the lambert beers law and determine the conc. Of kmno4

Answer 1

AIM: To verify Lambert – beer ‘s law for KMnO4colorimetrically.

THEORY

The primary objective of this experiment is to determine the concentration of an

unknown KMnO4 solution. The KMnO4 solution used in this experiment has a blue

color, so Colorimeter users will be instructed to use the red LED. A higher

concentration of the colored solution absorbs more light (and transmits less) than a

solution of lower concentration.

You will prepare five of known concentration (standard solutions).

Each solution is transferred to a small, rectangular cuvette that is placed into the

Colorimeter or Spectrometer. The amount of light hat pene ra es the s lution and strikes the

photocell is used to compute the absorbance of each solu on. When you graph absorbance

vs. concentration for the standard solutions, a direct relationship should result. The direct

relationship between absorbance

and concentration for a solution is known s Beer’s law.

You will determine the concentr tion of n unknown KMnO4 solution by measuring its

absorbance. By locating the absorba nce of the unknown on the vertical axis of the

graph, the

corresponding concentration can be found on the horizontal axis. The concentration

of the unknown can a so be found using the slope of the Beer’s law curve.

REQUIREMENTS

Colorimeter cuvette

five 20 × 150 mm test tubes

two 10 mL pipets or graduated cylinders two 100 mL beakers

0. 01M KMnO4 solution

distilled water test tube rack stirring rod

tissues (preferably lint-free)