Investigation of the beer - Lambert law Lab Report

Investigation of the beer - Lambert law - Lab Report Example It illustrated in the diagram below. Beer-Lambert law states that the absorbance is directly proportional to the concentration of the solution. It relates the absorbance of sample (A) to the concentration of the substance in the solution absorbing it and the path length of the light. Incident light from a tungsten or deuterium lamp is focused through a lens and passed through a slit. Passing the beam through the wavelength selector diffracts it separating it into light of a single wavelength. This particular wavelength is selected and exits through the slit. The light passing through the sample is detected by the photo detector which then converts it into an electrical current measured by the galvanometer. The reading is then sent to a read-out device. The plot of absorbance of light at different wavelengths is called it absorption spectrum. Fig. 1 gives the absorption spectrum of potassium permanganate (KMnO4 ). According to Beer-Lambert law, absorbance is directly proportional to concentration. This is clearly illustrated by Fig. 4. This is also known as a calibration curve. It should be drawn with utmost accuracy in order to obtain a straight line graph. The slope of this curve is equal to the absorbance of the potassium permanganate (Skoog, 45). One source of error is the use of inappropriate concentrations when applying Beer-Lambert law. It is only applicable for dilute solutions and becomes less accurate with increase in concentration. Another source of error is stray light or scattering within the instrument as this cause large errors especially when reading small values. The aim of the experiment was obtained because Beer-Lambert law was verified. Using linear regression analysis, Beer-Lambert law (A = ÃŽ µlc) implies that when concentration is equal to zero, absorbance must also be zero. This is a straight line equation passing through the origin hence the aim was achieved (Svanberg,