Measuring Rates of Reaction from a Graph

• How is the rate of reaction calculated?

  By dividing reactants used or products formed by time
• What is the rate of reaction if 1200 cm³ of hydrogen is produced in 4 minutes?

  240 cm³ per second
• Why does the average rate of reaction only provide limited information?

  It does not account for changes during the reaction
• What axes are used in the graph to measure reaction rates?

  X-axis for time, Y-axis for volume
• What does a steep curve on the graph indicate?

  A high rate of reaction
• How do you find the mean rate of reaction over three minutes?

  Divide hydrogen produced by time in seconds
• How do you calculate the actual rate at a specific time?

  By finding the gradient of the tangent at that point
• What is a tangent in the context of the graph?

  A line that touches the curve at one point
• How do you find the gradient of the tangent line?

  Change in volume divided by change in time
• What is the change in volume of hydrogen at two minutes?

  Approximately 600 cm³
• What is the significance of the tangent's length when calculating rates?

  Longer tangents provide more accurate values
• What is the starting point for a graph plotting magnesium remaining?

  The initial grams used in the reaction
• What should you remember about drawing tangents for exams?

  Examiners allow small variations in judgment
• What are the steps to calculate the mean rate of reaction from a graph?

  1. Identify the time interval on the x-axis.
  2. Draw a dashed line to intersect the curve.
  3. Find the corresponding volume on the y-axis.
  4. Divide the volume by the time in seconds.
• What are the steps to calculate the actual rate of reaction at a specific time?

  1. Identify the specific time on the x-axis.
  2. Draw a tangent at the curve's intersection.
  3. Measure the change in volume (y-axis).
  4. Measure the change in time (x-axis).
  5. Calculate the gradient: change in volume/change in time.