We performed an experiment on UV-Vis Spectrometry, by testing the absorbance of KMnO4 and KCr2O7 solutions at different concentrations. We prepared the dichromate solutions with dilute sulfuric acid. Why didn't we use water, what is the purpose of sulfuric acid?
When conducting an experiment on UV-Vis spectrometry, the choice of solvent plays an important role in determining the accuracy and reliability of the measurements. In this case, sulfuric acid is used instead of water for a specific purpose.
The purpose of using dilute sulfuric acid as the solvent when preparing the dichromate solutions is twofold:
1. Enhancing solubility: Some compounds, such as KMnO4 and KCr2O7, have limited solubility in water. By adding a small amount of sulfuric acid, the solubility of these compounds increases significantly. Sulfuric acid acts as a solubilizing agent, helping to dissolve and disperse the dichromate salts in the solvent more effectively.
2. Acidifying the solution: Sulfuric acid's primary role is to provide an acidic environment for the experiment. The acid medium is necessary to ensure the stability of the dichromate ions in solution. In an acidic medium, the dichromate ions (Cr2O7^2-) remain stable, allowing for accurate and consistent measurements of absorbance.
By using sulfuric acid as the solvent and creating an acidic environment, you are able to maximize the solubility of the dichromate compounds and maintain the stability of the dichromate ions in solution. This ensures reliable UV-Vis spectrometry measurements and accurate analysis of the absorbance of KMnO4 and KCr2O7 solutions at different concentrations.