N/10 Sodium Thiosulfate Solution Preparation and Standardization with K2Cr2O7 | Iodometric titration

Summary

This video tutorial demonstrates the preparation and standardization of sodium thiosulphate solution using potassium dichromate. The process involves weighing 2.48 grams of sodium thiosulphate and diluting it to 100 ml, followed by preparing a potassium dichromate solution with 0.49 grams in 100 ml. The video then details the titration process, including the addition of potassium iodide and HCl, and the use of starch indicator to determine the endpoint. The final step shows how to calculate the normality of the sodium thiosulphate solution and prepare an n by 80 hypo solution by dilution.

Takeaways

• 🧪 Sodium thiosulfate solution is prepared by weighing 2.48 grams of pentahydrated sodium thiosulfate and dissolving it in 100 ml of distilled water.
• 🔬 The prepared sodium thiosulfate solution is standardized using potassium dichromate, with 0.49 grams of potassium dichromate dissolved in 100 ml of distilled water.
• 🧼 All glassware, including burets and conical flasks, must be thoroughly rinsed before use to ensure accurate results.
• 📏 The titration process involves filling the buret with sodium thiosulfate solution and transferring 25 ml of potassium dichromate to a conical flask.
• 🧴 Potassium iodide and concentrated HCl are added to the potassium dichromate solution, which liberates iodine and changes the solution's color.
• 🧫 The titration continues by adding sodium thiosulfate to the flask until the dark brown color fades, followed by starch solution to form a starch-iodine complex.
• ⚗️ The titration is complete when the iodine's blue color disappears, and a pale color appears due to chromium ions.
• 📊 Observations include an initial buret reading of 0 ml and a final reading of 25 ml, indicating that 25 ml of sodium thiosulfate was consumed.
• 📝 The normality equation (N1V1 = N2V2) is used to calculate the normality of sodium thiosulfate, confirming it as N/10.
• 🌡️ To prepare N/80 sodium thiosulfate, 12.5 ml of N/10 sodium thiosulfate is diluted in a 100 ml measuring flask using distilled water.

Q & A

What is the purpose of preparing a sodium thiosulphate solution in the video?

The purpose is to prepare a sodium thiosulphate solution and standardize it using potassium dichromate.

How much sodium thiosulphate is used to prepare the solution in the video?

2.48 grams of sodium thiosulphate pentahydrate is used.

What is the final volume of the sodium thiosulphate solution prepared in the video?

The final volume of the sodium thiosulphate solution is 100 ml.

How is the sodium thiosulphate dissolved in the video?

It is dissolved by transferring the weighed amount to a measuring flask, rinsing the beaker properly, and shaking well to dissolve it into distilled water.

What is the concentration of the prepared sodium thiosulphate solution in the video?

The concentration of the prepared sodium thiosulphate solution is n by 10.

How much potassium dichromate is used to prepare its solution in the video?

0.49 grams of potassium dichromate is used.

What is the volume of the potassium dichromate solution prepared in the video?

The volume of the potassium dichromate solution is 100 ml.

Why is it necessary to rinse the glassware before standardizing the solution in the video?

Rinsing the glassware is necessary to ensure that there is no contamination that could affect the accuracy of the standardization process.

What is the initial reading of the burette when potassium dichromate is added in the video?

The initial reading of the burette is zero.

How much potassium iodide is added to the conical flask in the video?

0.5 grams of potassium iodide is added to the conical flask.

What color change is observed after adding concentrated HCl to the conical flask in the video?

After adding concentrated HCl, the color changes to indicate the liberation of iodine.

How is the endpoint of the titration determined in the video?

The endpoint of the titration is determined by the disappearance of the color of the starch-iodine complex after adding a few drops of starch solution.

What is the final reading of the burette after the titration in the video?

The final reading of the burette is about 25 ml.

How is the normality of the sodium thiosulphate solution calculated in the video?

The normality is calculated using the normality equation N1V1 = N2V2, where N1 and V1 are the normality and volume of potassium dichromate, and N2 and V2 are the normality and volume of sodium thiosulphate.

What is the normality of the hypo solution prepared by dilution in the video?

The normality of the hypo solution prepared by dilution is n by 80.

How much volume of n by 10 sodium thiosulphate solution is taken to prepare n by 80 hypo solution in the video?

12.5 ml of n by 10 sodium thiosulphate solution is taken to prepare 100 ml of n by 80 hypo solution.