Determine the Percentage Composition Volumetrically of a Solution Mixture of K2C2O4 and K2SO4

Abstract

In this experiment, the percentage composition of a solution mixture of potassium oxalate (K₂C₂O₄) and potassium sulfate (K₂SO₄) is determined volumetrically.

Introduction

The experiment aims to determine the percentage composition of a solution mixture containing potassium oxalate and potassium sulfate. This is achieved by titrating the solution mixture with a standardized solution of potassium permanganate (KMnO₄) and then performing calculations based on the titration results.

Experiment Details

Procedure:

1. Prepare a standardized solution of potassium permanganate (KMnO₄) by titrating it against a primary standard substance.
2. Measure a known volume of the solution mixture containing potassium oxalate and potassium sulfate.
3. Titrate the solution mixture with the standardized KMnO₄ solution until a faint pink color persists.
4. Record the initial and final burette readings to determine the volume of KMnO₄ solution used in the titration.

Observations and Calculation:

Based on the volume of KMnO₄ solution used in the titration and its concentration, calculate the moles of KMnO₄ used. Then, use stoichiometry to relate the moles of KMnO₄ to the moles of oxalate ions (C₂O₄^2-) in the solution mixture. Finally, calculate the percentage composition of potassium oxalate and potassium sulfate in the solution mixture.

1. Calculate the moles of KMnO₄ used:
   

   Use the formula:

   \( \text{{Moles of KMnO4}} = \text{{Molarity of KMnO4}} \times \text{{Volume of KMnO4 solution used in titration (in liters)}} \)

2. Use stoichiometry to relate moles of KMnO₄ to moles of oxalate ions (C₂O₄^2-):
   

   Refer to the balanced chemical equation of the reaction between KMnO₄ and oxalate ions. Typically, the equation is:

   \( \text{5C}_2\text{O}_4^{2-} + 2\text{MnO}_4^- + 16\text{H}^+ \rightarrow 2\text{Mn}^{2+} + 10\text{CO}_2 + 8\text{H}_2\text{O} \)

   From this equation, determine the stoichiometric ratio between KMnO₄ and C₂O₄^2-.

3. Calculate moles of oxalate ions:
   

   Use the stoichiometric ratio obtained in step 2 to calculate the moles of oxalate ions.

4. Determine the percentage composition of potassium oxalate and potassium sulfate:
   

   Use the moles of oxalate ions calculated in step 3, and the initial volume and concentration of the solution mixture, to determine the percentage composition of potassium oxalate and potassium sulfate in the solution mixture.

   1. Calculate the moles of oxalate ions (\( C_2O_4^{2-} \)):
      

      Use the stoichiometric ratio obtained in step 2 to calculate the moles of oxalate ions.

   2. Determine the moles of potassium oxalate (\( K_2C_2O_4 \)) and potassium sulfate (\( K_2SO_4 \)):
      

      Based on the balanced chemical equation, determine the moles of potassium oxalate and potassium sulfate present in the solution mixture.

   3. Calculate the mass of potassium oxalate (\( K_2C_2O_4 \)) and potassium sulfate (\( K_2SO_4 \)):
      

      Use the molar masses of potassium oxalate and potassium sulfate to calculate their respective masses.

   4. Determine the percentage composition:
      

      Divide the mass of each compound by the total mass of the solution mixture and multiply by 100\% to obtain the percentage composition of potassium oxalate and potassium sulfate.

Conclusion:

The experiment successfully determined the percentage composition of the solution mixture containing potassium oxalate and potassium sulfate. The calculated values provide insights into the relative concentrations of the two substances in the solution.

Precautions:

• Ensure accurate measurement of volumes using calibrated glassware.
• Avoid contamination of solutions to prevent inaccurate results.
• Handle chemicals with care and follow safety protocols.

Short Questions and Answers

1. What is the objective of determining the percentage composition of a solution mixture?
   

   The objective is to quantify the relative amounts of different substances present in the mixture.

2. Which substances are involved in the solution mixture in this experiment?
   

   The solution mixture contains potassium oxalate (K₂C₂O₄) and potassium sulfate (K₂SO₄).

3. What is the role of potassium permanganate (KMnO₄) in the titration?
   

   Potassium permanganate is used as the titrant to react with the analyte (solution mixture) and determine its composition volumetrically.

4. How is the endpoint of the titration determined?
   

   The endpoint is determined when a color change occurs, typically from pink to colorless, indicating the completion of the reaction.

5. What calculations are performed to determine the percentage composition of the solution mixture?
   

   The calculations involve determining the moles of reactants and products involved in the reaction, and then using stoichiometry to calculate the percentage composition.

6. Why is it important to use a standardized solution of KMnO₄?
   

   Using a standardized solution ensures accurate and reproducible results, as its concentration is precisely known.

7. What precautions should be taken to ensure accurate results in the experiment?
   

   Precautions include using calibrated glassware, avoiding contamination of solutions, and following safety protocols when handling chemicals.

8. What primary standard substance can be used for the standardization of KMnO₄?
   

   Oxalic acid (H₂C₂O₄) is commonly used as a primary standard for the standardization of KMnO₄.

9. What is the significance of recording initial and final burette readings during titration?
   

   Recording these readings allows the volume of titrant used in the titration to be determined accurately.

10. How can contamination affect the accuracy of results?
    

    Contamination can introduce additional substances into the solution, leading to errors in concentration calculations and inaccurate results.

11. What is the color change observed at the endpoint of the titration?
    

    The color change is typically from pink to colorless.

12. What is the stoichiometry of the reaction between KMnO₄ and oxalate ions?
    

    The stoichiometry of the reaction is determined by the balanced chemical equation representing the reaction between KMnO₄ and oxalate ions.

13. What equipment is used for precise measurement of volumes in the experiment?
    

    Pipettes and burettes are commonly used for precise measurement of volumes.

14. What is the purpose of acidifying the solution mixture before titration?
    

    Acidifying the solution ensures suitable conditions for the reaction between the titrant and analyte and prevents interference from other reactions.

15. How are moles of KMnO₄ related to moles of oxalate ions in the solution mixture?
    

    The balanced chemical equation of the reaction allows for the determination of the stoichiometric relationship between the two substances.

16. What units are commonly used for expressing concentration?
    

    Common units of concentration include molarity (M), molality (m), and normality (N).

17. Why should chemicals be handled with care in the laboratory?
    

    Chemicals should be handled with care to prevent accidents, ensure safety, and avoid contamination of solutions.

18. What is the role of sulfuric acid in the titration?
    

    Sulfuric acid is added to the solution to acidify it, providing suitable conditions for the reaction between the titrant and analyte.

19. What is the significance of performing multiple titrations?
    

    Performing multiple titrations helps ensure the reproducibility and accuracy of results by identifying and correcting any errors.

Multiple Choice Questions (MCQs)

1. What is the purpose of titrating the solution mixture with potassium permanganate (KMnO₄)?
   • a) To determine the acidity of the solution
   • b) To calculate the concentration of potassium sulfate
   • c) To determine the percentage composition of the solution mixture
   • d) To neutralize the solution
   Answer: c) To determine the percentage composition of the solution mixture
2. What is the color change observed at the endpoint of the titration?
   • a) Blue to colorless
   • b) Pink to colorless
   • c) Yellow to red
   • d) Green to brown
   Answer: b) Pink to colorless
3. Which precaution is essential to ensure accurate results in the experiment?
   • a) Using dirty glassware
   • b) Heating solutions rapidly
   • c) Avoiding contamination of solutions
   • d) Neglecting to record initial and final burette readings
   Answer: c) Avoiding contamination of solutions
4. What is the role of sulfuric acid in the titration?
   • a) To provide color to the solution
   • b) To neutralize the solution
   • c) To prevent oxidation of potassium oxalate
   • d) To prevent oxidation of potassium permanganate
   Answer: c) To prevent oxidation of potassium oxalate
5. Which substance is used as a primary standard for the standardization of potassium permanganate (KMnO₄) solution?
   • a) Potassium sulfate (K₂SO₄)
   • b) Potassium oxalate (K₂C₂O₄)
   • c) Sodium chloride (NaCl)
   • d) Sulfuric acid (H₂SO₄)
   Answer: b) Potassium oxalate (K₂C₂O₄)