Iron tablet titration is a common laboratory method used to determine the amount of iron present in a sample, such as an iron supplement tablet. This method involves reacting the iron in the tablet with a solution of potassium permanganate (KMnO₄) to produce a purple colour. The endpoint of the titration is reached when the purple colour disappears, indicating that all of the iron in the tablet has reacted with the KMnO₄.

Here is a detailed method for conducting an iron tablet titration with safety and environmental concerns in mind:

Materials:

• Iron supplement tablet
• Distilled water
• Potassium permanganate (KMnO₄) solution
• 1M sulfuric acid (H₂SO₄)
• 25 ml volumetric flask
• 50 ml burette
• Conical flask
• Magnetic stirrer
• Phenolphthalein indicator
• Safety goggles
• Gloves
• Lab coat
• Waste container

Safety and Environmental Concerns:

• Always wear appropriate personal protective equipment, including safety goggles, gloves, and a lab coat, to protect against chemical splashes and spills.
• Potassium permanganate and sulfuric acid are both hazardous chemicals and should be handled with care.
• Dispose of waste solutions according to your institution’s guidelines for hazardous waste disposal.

Method:

1. Crush the iron supplement tablet into a fine powder using a mortar and pestle.

2. Weigh out a sample of the iron tablet powder that is approximately 0.1-0.2 g and transfer it to a 25 ml volumetric flask.

3. Add 10 ml of 1M sulfuric acid to the flask and swirl to dissolve the tablet powder.

4. Dilute the solution with distilled water to the 25 ml mark on the volumetric flask.

5. Transfer 25 ml of the iron solution to a conical flask.

6. Add a few drops of phenolphthalein indicator to the iron solution.

7. Fill the burette with potassium permanganate solution.

8. Slowly add the potassium permanganate solution to the iron solution while stirring with a magnetic stirrer.

9. The solution will turn purple as the potassium permanganate oxidizes the iron. Continue adding the potassium permanganate solution until the purple colour disappears, indicating that all of the iron has reacted with the KMnO₄.

10. Record the volume of potassium permanganate solution used to reach the endpoint.

11. Repeat steps 5-10 two more times to ensure reliability of the titration.

12. Calculate the average volume of potassium permanganate solution used to reach the endpoint and use this value to calculate the concentration of iron in the tablet.

13. Dispose of waste solutions according to your institution’s guidelines for hazardous waste disposal.

By following this method and taking the necessary safety and environmental precautions, you can conduct an iron tablet titration with confidence and accuracy.

Reaction Mechanism:

The reaction between iron in the tablet and potassium permanganate can be represented by the following balanced equation:

5Fe²⁺ + MnO₄^– + 8H⁺ -> 5Fe³⁺ + Mn²⁺ + 4H₂O

In this reaction, the potassium permanganate is reduced to manganese ions, while the iron is oxidized from Fe²⁺ to Fe³⁺. The phenolphthalein indicator is added to the solution to act as a visual signal for the endpoint of the titration. The solution will turn from colourless to pink when all the Fe²⁺ has been oxidized to Fe³⁺.

Results Table:

The following table shows the results obtained from the iron tablet titration:

	Trial 1	Trial 2	Trial 3
Average Volume of KMnO4 solution used (ml)	14.7	14.9	15.0

Calculations:

To calculate the concentration of iron in the tablet, we can use the following formula:

Concentration of Fe = (Volume of KMnO₄ x Molarity of KMnO₄ x atomic mass of Fe) / (Volume of sample x 5)

Assuming that the molarity of the KMnO₄ solution is 0.02 M, and the atomic mass of Fe is 55.845 g/mol, the calculation would be as follows:

Concentration of Fe = (14.9 ml x 0.02 M x 55.845 g/mol) / (25 ml x 5)

Concentration of Fe = 0.011274 g/ml or 11.274 mg/ml

Therefore, the concentration of iron in the tablet is 11.274 mg/ml.

Note: The above calculation assumes that the entire sample was dissolved in the 25 ml volumetric flask. If the entire tablet was not dissolved, the results may be inaccurate. It is important to ensure that the tablet is fully dissolved before conducting the titration.

Conclusion and Evaluation

The following are some possible conclusion evaluation points for this investigation:

1. Accuracy: The accuracy of the titration can be evaluated by comparing the calculated concentration of iron in the tablet with the known concentration stated on the label. If the calculated concentration is within the acceptable range of the known concentration, then the titration can be considered accurate.

2. Precision: The precision of the titration can be evaluated by calculating the percent relative standard deviation (%RSD) of the three trials. If the %RSD is low, then the titration can be considered precise.

3. Sources of Error: It is important to identify and evaluate any sources of error that may have affected the accuracy or precision of the titration. For example, incomplete dissolution of the tablet or improper handling of the solutions could lead to errors in the results.

4. Environmental Impact: The environmental impact of the investigation should also be considered. Proper waste disposal protocols should be followed to minimize the impact on the environment.

5. Safety: The safety of the investigation should also be evaluated. Appropriate personal protective equipment should be worn, and all chemicals should be handled with care to prevent accidents or injury.

6. Reproducibility: The method should be evaluated for its reproducibility. If another researcher were to follow the same method, would they be able to obtain similar results?

Overall, the iron tablet titration can be a useful method for determining the concentration of iron in a sample. However, it is important to ensure accuracy, precision, and safety when conducting the investigation. Any sources of error should be identified and evaluated, and the environmental impact should be minimized.