3

• What is the reaction investigated in Required Practical 3?

  Reaction of sodium thiosulphate with hydrochloric acid
• What is the purpose of the disappearing cross experiment?

  To observe how temperature affects reaction rate
• What is the balanced equation for the reaction?

  [Na​2​S​2​O​3​ + 2HCl → 2NaCl + SO​2​ + S + H​2​O]
• What are the steps in the method for the experiment?

  1. Add hydrochloric acid to the acid tube.
  2. Add sodium thiosulfate to the second tube.
  3. Record start temperature, add acid, and time.
  4. Record time for cross to disappear.
  5. Measure final temperature and pour contents into sodium carbonate.
  6. Adjust water temperature in the container.
  7. Repeat for different temperatures.
• What is the concentration of hydrochloric acid used?

  1 mol dm​-3
• What is the concentration of sodium thiosulfate used?

  0.05 mol dm​-3
• Why is it important to measure the initial and final temperature accurately?

  To find a mean temperature for the reaction
• What should the maximum temperature of the water be?

  55 °C
• What safety measures should be taken during the experiment?

  Wear eye protection, lab coat, and gloves
• What is the purpose of the stop baths in the experiment?

  To neutralize acid and sulfur dioxide
• What should be done when the color of the stop bath changes?

  • Sodium carbonate has been used up.
  • The stop bath needs to be replenished.
• How does the concentration of reactants affect the experiment?

  Concentrations remain the same throughout the experiment
• What does the time taken to produce sulfur indicate?

  It indicates the rate of the reaction
• What is the relationship between initial rate of reaction and time?

  Initial rate is proportional to 1/time
• What assumptions are made about the amount of sulfur produced?

  • The amount of sulfur produced is fixed.
  • The amount of sulfur is constant throughout the experiment.
• What is the purpose of using a fume cupboard during the experiment?

  To minimize exposure to toxic sulfur dioxide
• Why is it important to conduct the investigation in a well-ventilated room?

  To ensure safety from toxic fumes
• What should be done with waste solutions after the experiment?

  Dispose of them appropriately
• What data can be plotted from the experiment results?

  • Amount of sulfur produced
  • Time taken for the reaction
• What is the significance of plotting a graph of sulfur produced against time?

  It helps visualize the reaction rate
• What is the initial rate of reaction formula?

  Initial rate = amount of sulfur/time
• Why is the approximation for rate of reaction used?

  It simplifies calculations without concentration
• What are the key components of the experiment's setup?

  • Acid tube with hydrochloric acid
  • Tube with sodium thiosulfate
  • Plastic container for temperature control
  • Thermometer for measuring temperature