Absorbance and Spectrophotometry
Experiment 2: Absorbance and Spectrophotometry
ABSTRACT:
This was an investigation into the effects of different wavelengths of light on methylene blue and carmine red on the absorbance value on a spectrophotometer. A spectrophotometer is used to measure light intensity by emitting a single light source through a cuvette of coloured solution. The particles in the solution, which are coloured, absorb the light depending on how concentrated it is and this produces an electronic reading from the photometer which is the absorbance value. The maximum absorption was found for both solutions and was used to calculate the molar extinction coefficient of methylene blue. An unknown concentration of methylene blue was calculated by using graphs produced in the dilution experiments prior. The results produced supported Beer’s Law because the absorbance was directly proportional to the concentration, and so, we can be assured that the concentration of the unknown methylene blue solution calculated is relatively accurate.
INTRODUCTION:
A spectrophotometer is used to measure the absorbance of light by coloured solutions. The absorbance value is produced by a photometer that compares the light detected with a blank cuvette (a cuvette containing just water/clear colourless solvent, which should be 0), with the amount of light detected with a test solution – in this case, methylene blue or carmine red. Using Beer’s Law, we know that the absorbance is directly proportional to the concentration, therefore, knowing the absorbance of a solution can be very useful as the concentration of the solution can be find by substituting known values into the equation:
Absorbance = k c t
Where: k = constant c = concentration of absorbing molecules t = thickness of absorbing layer
The aims of this experiment were to use solutions methylene blue and carmine red to confirm that Beer’s Law is true by finding the maximum absorption value for each solution, and then
ABSTRACT:
This was an investigation into the effects of different wavelengths of light on methylene blue and carmine red on the absorbance value on a spectrophotometer. A spectrophotometer is used to measure light intensity by emitting a single light source through a cuvette of coloured solution. The particles in the solution, which are coloured, absorb the light depending on how concentrated it is and this produces an electronic reading from the photometer which is the absorbance value. The maximum absorption was found for both solutions and was used to calculate the molar extinction coefficient of methylene blue. An unknown concentration of methylene blue was calculated by using graphs produced in the dilution experiments prior. The results produced supported Beer’s Law because the absorbance was directly proportional to the concentration, and so, we can be assured that the concentration of the unknown methylene blue solution calculated is relatively accurate.
INTRODUCTION:
A spectrophotometer is used to measure the absorbance of light by coloured solutions. The absorbance value is produced by a photometer that compares the light detected with a blank cuvette (a cuvette containing just water/clear colourless solvent, which should be 0), with the amount of light detected with a test solution – in this case, methylene blue or carmine red. Using Beer’s Law, we know that the absorbance is directly proportional to the concentration, therefore, knowing the absorbance of a solution can be very useful as the concentration of the solution can be find by substituting known values into the equation:
Absorbance = k c t
Where: k = constant c = concentration of absorbing molecules t = thickness of absorbing layer
The aims of this experiment were to use solutions methylene blue and carmine red to confirm that Beer’s Law is true by finding the maximum absorption value for each solution, and then