Measure+calculate rate of reaction

• What is the purpose of measuring rates of reaction?

  To quantify how fast reactions occur
• How can the rate of a reaction be observed?

  By measuring reactants used or products formed
• What is the formula for calculating the rate of reaction?

  Rate of Reaction = Amount / Time
• What units are used for measuring gas in reactions?

  cm³
• What units are used for measuring solids in reactions?

  grams (g)
• What is the time unit commonly used in measuring reaction rates?

  seconds (s)
• What are the possible units for rate of reaction?

  cm³/s, g/s, or moles/s
• What are the three methods to measure the rate of a reaction?

  1. Precipitation and Colour Change
  2. Change in Mass (Usually Gas Given Off)
  3. The Volume of Gas Given Off
• How can precipitation and colour change indicate reaction rate?

  By observing visual changes in the solution
• What does a faster disappearance of a mark indicate in a reaction?

  The reaction rate is faster
• What is a disadvantage of using the precipitation method?

  Results are subjective and hard to quantify
• How is the change in mass method used to measure reaction rates?

  By measuring mass loss on a balance
• What is the advantage of using a mass balance in measuring reaction rates?

  It provides accurate mass measurements
• What is a potential issue when using the mass balance method?

  Gas is released into the room
• How does the volume of gas given off method work?

  By using a gas syringe to measure gas volume
• What is a risk when using a gas syringe?

  The plunger can blow out if too vigorous
• What are the steps for the magnesium and HCl reaction experiment?

  1. Add dilute HCl to a conical flask.
  2. Weigh the flask on a mass balance.
  3. Add magnesium ribbon and plug with cotton wool.
  4. Start the stopwatch and record mass at intervals.
  5. Plot results and graph mass loss against time.
• What should be kept constant in the magnesium and HCl experiment?

  Amount of magnesium and volume of acid
• What does a higher concentration of acid indicate in the reaction rate?

  It results in a faster rate of reaction
• What are the steps for the sodium thiosulfate and HCl experiment?

  1. Add dilute sodium thiosulfate to a conical flask.
  2. Place flask over a black cross.
  3. Add dilute HCl and start the stopwatch.
  4. Time how long until the cross disappears.
  5. Repeat with different concentrations of reactants.
• Why should the sodium thiosulfate and HCl experiment be conducted in a well-ventilated area?

  Because it releases sulfur dioxide gas
• What is the relationship between concentration of HCl and time taken for the mark to disappear?

  Higher concentration results in shorter time
• How can mean reaction rates be calculated from a graph?

  1. Identify the overall change in y-value.
  2. Divide by the total time taken.
  3. Can also find rates for specific periods.
• How do you find the mean rate of reaction between two time points?

  Calculate change in y divided by change in x
• What is the method to find the reaction rate at a specific point on a graph?

  1. Draw a tangent at the point.
  2. Calculate the gradient of the tangent.
  3. Use two points on the tangent for calculation.
• How do you calculate the gradient of a tangent?

  Change in y divided by change in x
• What was the example mean rate of reaction calculated in the text?

  0.2 cm³/s
• What was the rate of reaction at 3 minutes in the example?

  0.27 g/min