Graph: Absorbance vs Wavelength
The absorption of light by a substance is a fundamental property that can provide valuable information about its composition and behavior. In this experiment, we investigated the relationship between absorbance and wavelength using a spectrophotometer.
1. We prepared a series of standard solutions with known concentrations of a compound.
2. Using a spectrophotometer, we measured the absorbance of each solution at various wavelengths ranging from 200 nm to 800 nm.
3. The data obtained was used to plot a graph of absorbance against wavelength.
The graph of absorbance versus wavelength revealed several important trends. Firstly, there was a significant peak at a specific wavelength for each concentration of the solution. This peak corresponded to the maximum absorbance of light by the compound.
Secondly, as the concentration of the solution increased, the peak absorbance also increased. This indicated a direct relationship between concentration and absorbance.
Thirdly, we observed that absorbance gradually decreased as the wavelength moved away from the peak. This suggested that the compound had a specific range of absorption, with lower absorbance at both shorter and longer wavelengths.
The relationship between absorbance and wavelength can be attributed to the electronic structure of the compound. Different compounds have different electronic transitions that occur at specific wavelengths. As a result, they absorb light selectively, leading to distinctive absorbance patterns.
The direct relationship between concentration and absorbance is described by the Beer-Lambert Law, which states that absorbance is directly proportional to the concentration of the absorbing species. This law holds true as long as the solution is not saturated and the path length remains constant.
The gradual decrease in absorbance as the wavelength moves away from the peak can be explained by the absorption spectrum of the compound. Each compound has a unique absorption spectrum, which is determined by the energy levels of its electronic transitions. Absorption decreases at wavelengths where the compound’s electronic transitions are less likely to occur.
Through this experiment, we have demonstrated the relationship between absorbance and wavelength using a graph. The graph showed distinct absorbance peaks at specific wavelengths, with higher concentrations resulting in greater absorbance. Additionally, absorbance gradually decreased as the wavelength moved away from the peak. Understanding the relationship between absorbance and wavelength is crucial in fields such as chemistry and biology, as it allows for the identification and quantification of various compounds in a sample.