rate of reaction

• What reaction is used in the disappearing cross experiment?

  Sodium thiosulfate with hydrochloric acid
• What does turbidity refer to in a solution?

  Cloudiness caused by suspended particles
• How do you start the disappearing cross experiment?

  Swirl the solution and start a stopwatch
• When do you stop the stopwatch in the disappearing cross experiment?

  When the cross is no longer visible
• What should you do with anomalous results when calculating the mean?

  Do not include them in the calculation
• What does reproducibility mean in measurements?

  Results can be repeated with the same outcome
• What is a problem with the disappearing cross experiment?

  Different eyesight affects visibility of the cross
• What is the second method for the required practical?

  Measuring the volume of gas produced
• What gas is produced when magnesium reacts with hydrochloric acid?

  Hydrogen gas
• How do you measure the volume of hydrogen gas produced?

  Using a measuring cylinder over a delivery tube
• What should you do every 10 seconds during the gas measurement experiment?

  Measure the volume of hydrogen gas
• What happens to the reaction rate with greater concentration?

  The reaction occurs faster
• Why can we say the finding about concentration and reaction rate is reproducible?

  It is shown by two different experiments
• What are the steps for the disappearing cross experiment?

  1. Measure 10 cm³ sodium thiosulfate in a flask.
  2. Place the flask on a printed black cross.
  3. Add 10 cm³ hydrochloric acid and swirl.
  4. Start the stopwatch.
  5. Stop when the cross is no longer visible.
  6. Repeat with lower concentrations and calculate mean values.
• What are the steps for measuring gas volume with magnesium and hydrochloric acid?

  1. Measure 50 cm³ hydrochloric acid in a flask.
  2. Attach a delivery tube to the flask.
  3. Place the tube in water with an upturned measuring cylinder.
  4. Add a 3 cm strip of magnesium to the acid.
  5. Start the stopwatch and measure gas volume every 10 seconds.
  6. Repeat with different concentrations of hydrochloric acid.