Redox Titration Experiment

Jul 12, 2024

Redox Titration Experiment

Overview

  • Experiment Number: Five
  • Previous Experiment: Acid-Base Titration
  • Current Focus: Redox Reaction
    • Involves: Oxidizing and Reducing Agents
    • Essence: Transfer of electrons

Steps of the Experiment

Step 1: Acidifying Sodium Hypochlorite

  • Reactants: Sodium Hypochlorite (NaOCl) and Hydrochloric Acid (HCl)
  • Product: Hypochlorous Acid (HOCl)
  • Condition: Acidic Medium is necessary
    • Addition of HCl ensures this

Step 2: Redox Reaction

  • Reactants: Hypochlorous Acid (HOCl) and Iodide (I-)
  • Products: Triiodide (I3-), Chloride (Cl-), and Water (H2O)
  • Role of Products: I3- complexes with starch forming a dark blue color

Step 3: Titration with Sodium Thiosulfate

  • Titrant: Sodium Thiosulfate (Na2S2O3)
  • Indicator: Starch (Complexed with I3-)
  • Aim: To reach equivalence point (color change from dark blue to colorless)

Calculations

  • Molarity and Volume Relationship: [Molarity = \frac{Moles}{Volume}]
  • **Steps: **
    • Determine molarity of Na2S2O3
    • Measure volume of titrant from burette (convert to liters)
    • Use stoichiometry to find moles of NaOCl and I3-
    • Proceed through stoichiometric steps: find moles to grams using molar mass
    • Calculate percent concentration: (% ) = (mass of NaOCl / total mass) x 100

Experimental Procedure

Sample Preparation

  1. Clorox Sample: Pipette 25.00 ml into 250 ml volumetric flask, then dilute to mark.
  2. Reagents Addition:
  • 15 ml distilled water
  • 20 ml 10% Potassium Iodide (KI)
  • 20 ml Hydrochloric Acid (HCl)
  • (Optional) 2 ml of starch solution

Burette Preparation

  1. Cleaned and Filled: Sodium Thiosulfate solution
  2. Zero Adjustment: Ensure bottom of meniscus aligns with zero mark

Titration Process

  1. Add Sodium Thiosulfate: Until pale yellow color achieved
  2. Add Starch Indicator: Solution turns dark blue
  3. Continue titration: Until color changes from dark blue to colorless (equivalence point)
  4. Volume Reading: Record final volume from burette

Conclusion and Data Handling

  • Volume Calculations: Initial and final readings
  • Stoichiometry: Use to find grams of NaOCl
  • Percent Concentration: Use density and volume to find final concentration

Tips and Reminders

  • Careful with volumes: Convert ml to liters for accuracy
  • No bubbles in burette: Ensure calibration for precise measurements
  • Repeat titration for consistency: Multiple trials recommended

Ending Note

  • Next video: Practical demonstration and data collection for calculations.

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