Cola Analysis

INTRODUCTION

The objective of the cola analysis lab is to measure the absorbance of a cola sample using a computer spectrometer to determine the phosphate concentration. The data collected in the experiment will be compared using a Beer’s Law plot. A Beer’s Law plot measures the proportionality of absorbance versus concentration. The linear equation derived from the data points can be used to determine the concentration of cola. There are two areas of concern in this lab that can affect the results in a negative way, the caramel color of the cola and the carbon dioxide found in the carbonated cola. To account for the caramel color a blank must be used to negate the color versus actual absorbance. To do this the blank is water and the sample is cola and water. The result is then subtracted from the actual sample (cola, water, and Molybdium vanadomolybdate (MoV)). The compound Molybdium vanadomolybdate (faint yellow) is used in this experiment because it reacts with phosphorous (colorless) resulting in a deep yellow coloration. This yellow color can then be used to measure the absorbance of the complex product using the violet region of the atomic spectrum (350-435 nanometers (nm)). To remove the fizz and bubbles caused by the carbon dioxide a simple method of pouring the cola between two beakers can be used. To get an accurate reading of the absorbance of cola, it must first be diluted with water to a certain concentration (5 milliliters (ml) cola to 100 ml water in this lab). In the first part of the lab the absorbance of the Molybdium vanadomolybdate and phosphate complex is measured using a serial dilution to develop a Beer’s Law plot of the absorbance versus concentration of the “complex”. The resulting standards (data points) are used to develop a linear equation of the line is used to determine the concentration of the diluted cola which in turn can be regressed to determine the initial concentration of cola. The percent transmittance can be used to...