Two Rates Experiments

• What is the focus of the practical investigations mentioned?

  Effect of concentration on reaction rate
• Why is the practical investigation described as "lovely"?

  It has two methods that can be used
• What are the steps to produce H₂ gas using magnesium and HCl?

  1. Add dilute hydrochloric acid to a conical flask.
  2. Quickly add magnesium ribbon to the acid.
  3. Plug the flask with cotton wool.
  4. Record the mass on a balance.
  5. Measure the gas produced over time.
• What should you wear during the experiment?

  Safety goggles
• What is the purpose of the stop watch in the experiment?

  To record the time taken for reactions
• How do you determine the mass loss during the reaction?

  By recording the mass at regular intervals
• What should you do with the results after plotting them in a table?

  • Analyze the mass lost for each reading
  • Plot a graph with time on the x-axis
  • Plot mass loss on the y-axis
• What happens to the reaction rate with higher acid concentration?

  It increases the reaction rate
• What should be kept constant during the experiment?

  The depth of the liquid must remain the same
• What do the results indicate about the relationship between acid concentration and reaction rate?

  Higher concentration leads to faster reactions
• What is the procedure for producing a cloud of precipitate using sodium thiosulfate and HCl?

  1. Add sodium thiosulfate to a conical flask.
  2. Place the flask on a piece of paper with a black cross.
  3. Add dilute hydrochloric acid to the flask.
  4. Start the stopwatch and observe the cross.
  5. Record the time taken for the cross to disappear.
• What color precipitate is formed in the reaction of sodium thiosulfate and HCl?

  Yellow precipitate of sulfur
• What does the disappearance of the cross indicate?

  The reaction has produced enough precipitate
• How can you ensure a fair test when repeating the experiment?

  Keep all variables constant except concentration
• What are the key variables to control in the experiments?

  • Volume of acid used
  • Amount of magnesium or sodium thiosulfate
  • Temperature of the reaction mixture
• What is the effect of increasing the concentration of HCl on the reaction rate?

  It increases the reaction rate
• Why is it important to measure the gas released accurately?

  To determine the reaction rate precisely
• What can be concluded from the results of the experiments?

  Higher acid concentration results in faster reactions
• What should only be changed in the experiment?

  The concentration of one reactant
• What must be kept constant during the experiment?

  The depth of the liquid
• What do the results show regarding HCl concentration?

  The effect on the reaction rate
• How does increasing HCl concentration affect the reaction?

  It increases the reaction rate
• What happens when sodium thiosulfate is added to the reaction?

  It creates a visible change over time
• What is the relationship between concentration and reaction time?

  Higher concentration leads to quicker reactions
• What does a set of readings indicate in this experiment?

  How long it took for the mark to disappear
• What is the effect of higher concentration on the time for the mark to disappear?

  It takes less time for the mark to disappear
• What factors should be kept constant in the experiment?

  • Temperature
  • Volume of reactants
  • Pressure of the system
• What is a limitation of the reaction described?

  It doesn't provide a set of graphs
• What should be done with the cotton wool in the flask?

  It should stop the acid from spilling out
• What is the concentration of HCl measured in?

  mol/dm³
• How can you visualize the concentration of HCl over time?

  By plotting concentration against time
• What does the reaction produce that is relevant to the experiment?

  Sulfur dioxide gas
• What is the significance of carrying out the experiment in a well-ventilated place?

  To ensure safety from gas exposure
• What is the time taken for the mark to disappear at 0.5 mol/dm³?

  1.93 seconds
• What is the time taken for the mark to disappear at 0.4 mol/dm³?

  1.04 seconds
• What is the time taken for the mark to disappear at 0.3 mol/dm³?

  1.68 seconds
• What is the time taken for the mark to disappear at 0.2 mol/dm³?

  2.47 seconds
• What is the time taken for the mark to disappear at 0.1 mol/dm³?

  3.34 seconds
• What are the key factors affecting reaction rate in this experiment?

  • Concentration of HCl
  • Presence of sodium thiosulfate
  • Temperature of the reaction
• How can you determine the rate of reaction from the experiment?

  By measuring the time for the mark to disappear