Rate of reaction observing colour change

• What affects the rate of reaction?

  Temperature, concentration, pressure, catalysts
• How does the frequency of successful collisions affect reaction rate?

  Higher frequency increases the reaction rate
• What is the aim of the core practical involving sodium thiosulfate and hydrochloric acid?

  • Investigate the effect of temperature on reaction rate
  • Use sodium thiosulfate and hydrochloric acid
• What is the chemical equation for the reaction between sodium thiosulfate and hydrochloric acid?

  Na₂S₂O₃ + 2HCl → 2NaCl + H₂O + SO₂ + S
• What observable change indicates the reaction has occurred?

  A cloudy yellow-white precipitate forms
• How do you measure the reaction time in the practical?

  Record time until the cross is no longer visible
• What should be recorded after mixing the reactants?

  Temperature of the reaction mixture
• What are the steps to investigate the rate of reaction?

  1. Add sodium thiosulfate to a flask
  2. Place flask over a marked cross
  3. Add hydrochloric acid and start timing
  4. Record temperature and time until cross disappears
  5. Clean apparatus and repeat with different temperatures
• What does the table of results show regarding temperature and reaction time?


  Higher temperatures lead to shorter reaction times
• How is the rate of reaction calculated from the results?

  Rate = $\frac{1000}{time}$
• What should be plotted on the graph to analyze the results?

  Reaction rate on the vertical axis, temperature on horizontal
• What happens to the rate of reaction as temperature increases?

  The rate of reaction increases
• Why should the same person observe the black cross each time?

  To ensure consistent visibility judgment
• What are the hazards and precautions in the experiment?

  Hazards:

  • Hot sodium thiosulfate solution
  • Sulfur dioxide

  
  

  Precautions:

  • Do not heat above 60°C
  • Ensure good ventilation
• What harm can hot sodium thiosulfate solution cause?

  Burns to the skin
• What harm can sulfur dioxide cause?

  Irritation to eyes and lungs
• What is a necessary precaution when handling sulfur dioxide?

  Ensure the laboratory is well ventilated
• What should you avoid when working with sulfur dioxide?

  Avoid breathing directly over the flask