Procedure for preparation and standardization 0.1 N Potassium Dichromate

1. OBJECTIVE
To lay down the procedure for preparation and standardization of 0.1 N Potassium Dichromate

2. SCOPE
This procedure is applicable to Quality Control Department

3. RESPONSIBILITY
• Officer QC
• Manager QC

4. SAFETY INSTRUCTIONS
• Proper handling the apparatus.
• It is recommended to wear gloves and protective eyewear when handling chemicals.
• Additionally, it is important to weigh the chemical accurately and dissolve it completely to ensure the desired concentration of the solution.

5. PROCEDURE
5.1 PREPARATION
5.1.1 Calculate the amount of Potassium Dichromate needed to prepare a 0.1 N solution by using the formula:
      grams of Potassium Dichromate = M x V (L) x EW

where M is the desired morality,can be calculated by dividing the normality of the solution by change in oxidation state, V is the volume of the solution to be prepared, and EW is the equivalent weight of Potassium Dichromate.

The equivalent weight of Potassium Dichromate is 49.03 g/equivalent (since To find equivalent weight of potassium dicromate, we must go through the change of oxidation state of Cr in the reactant and product as well in acid medium Cr2O7^-2→ 2 Cr^+3), Here oxidation state changed from (2×6 to 2×3, so the change is 6) the equivalent weight of K2Cr2O7 =294.18/6=49.03.).

      grams of Potassium Dichromate = 0.1 x 1 x 49.03 = 4.903 g

5.1.2 Weigh out 4.903gm of Potassium Dichromate using a balance.
5.1.3 After measuring the required amount, transfer it into a 1 liter volumetric flask.
5.1.4 Add a small amount of distilled water to the flask and swirl to dissolve.
5.1.5 Then fill up the flask with distilled water until the mark and mix well.
5.2 STANDARDIZATION
5.2.1 Transfer 25.0 mL of this solution to a glass-stoppered, 500-mL flask, add 2 g of potassium iodide (free from iodate), dilute with 200 mL of water, add 5 mL of hydrochloric acid.
5.2.2 Allow to stand for 10 minutes in a dark place, and titrate the liberated iodine with 0.1 N sodium thiosulfate VS, adding 3 mL of starch TS as the endpoint is approached.
5.2.3 Carry out a blank determination.
5.2.4 And calculate the normality by the following formula:

         ml Na₂S₂O₃ x N Na₂S₂O₃
N= ———————————————————–
         25

6. RELATED DOCUMENTS
N/A

7. DISTRIBUTION INDEX
Original Copy will be retained by Quality Assurance Department.

8. ABBREVIATIONS
Q.C Quality Control Department
TS Test Solution
Gm Gram
ml Milliliter

9. REVISION HISTORY