Video 3

Summary

This chemistry experiment demonstrates the process of COD (Chemical Oxygen Demand) analysis. It involves using a detergent wastewater sample and several reagents such as sulfuric acid, iron ammonium sulfate, and a digestion solution. The procedure includes mixing the sample with reagents, heating the solution, and performing a titration. During the experiment, changes in color indicate reactions, such as the transformation of Cr2O7^2- ions to Cr3+ ions, which helps determine the concentration of the contaminant. The final stage involves titrating the sample with a ferrous sulfate solution and observing a color change to identify the COD value.

Takeaways

• 😀 The experiment being conducted is titled 'COD Analysis' and is part of a Chemistry Analytical Lab.
• 😀 The materials needed for the experiment include wastewater sample (detergent waste), 0.05 Molar FAS (Ferrous Ammonium Sulfate), digestion solution, sulfuric acid reagent, and ferroin indicator.
• 😀 The necessary equipment includes a glass beaker, culture tube, pipettes, burette, stative, clamp, oil bath, and electric heater.
• 😀 The first step involves mixing the wastewater sample, digestion solution, and sulfuric acid reagent.
• 😀 2.5 mL of wastewater sample (detergent waste) is taken, followed by adding 1.5 mL of digestion solution and 3.5 mL of sulfuric acid reagent.
• 😀 During this step, a phenomenon occurs where the solution volume rises due to the chemical reaction.
• 😀 The mixture is then placed in a culture tube and heated in an oil bath at 150°C for 2 hours.
• 😀 A blank solution is also prepared by replacing the wastewater sample with aquades, which is then also heated.
• 😀 The color change observed during the reaction indicates the completion of the process. A yellow sample indicates the presence of Cr2O7²-, and a green color shows that Cr2O7²- has reacted completely into Cr3+.
• 😀 If the wastewater sample turns green after heating, it means the concentration of the sample is too high and the Cr2O7²- ion has been fully reduced.
• 😀 After heating, titration is performed by adding FAS solution and ferroin indicator, which results in a color change from yellow-green to reddish-brown.
• 😀 The final step involves noting the titration volume used in the experiment.

Q & A

What is the title of the experiment conducted in the script?

The title of the experiment is 'COD Analysis'.

What sample is used for the COD analysis in the experiment?

The sample used in the experiment is wastewater, specifically detergent wastewater.

What chemicals are needed for the experiment?

The chemicals required are a 0.05 Molar FAS (ferroammonium sulfate) solution, digestion solution, sulfuric acid, and Ferroing indicator.

What equipment is necessary for the experiment?

The necessary equipment includes a glass beaker, test tubes, pipettes, volumetric pipette, clamps, oil bath, and electric heater.

How is the initial mixture prepared in the experiment?

The initial mixture is prepared by combining 2.5 mL of detergent wastewater sample, 1.5 mL of digestion solution, and 3.5 mL of sulfuric acid.

What happens to the solution after adding sulfuric acid?

The solution experiences a noticeable phenomenon where the solution color changes and rises.

What is the procedure for preparing the blank solution?

The blank solution is prepared similarly to the wastewater mixture, but the detergent wastewater is replaced with aquadest (distilled water).

At what temperature and for how long is the mixture heated?

The mixture is heated in an oil bath at 150°C for about 2 hours.

What is the significance of the color change in the sample during heating?

A yellow sample that remains yellow after heating indicates the presence of Cr2O7^2- ions in the solution, while a sample that turns green shows that all Cr2O7^2- ions have reacted to form Cr^3+ ions.

What is the purpose of the titration in the experiment?

The titration is performed to determine the volume of the titrant used, with the color change indicating the endpoint of the reaction.

What color change occurs during the titration?

During the titration, the solution changes from a yellow-green color to a reddish-brown color.