How to Calculate the Rate of Reaction

• What is the purpose of using graphs in the video?

  To measure the mean rate of a reaction
• How is the rate of reaction calculated?

  By dividing reactants used or products formed by time
• If 1200 cm³ of hydrogen is produced in 4 minutes, what is the rate?

  5 cm³ per second
• Why does the reaction rate slow down over time?

  Because reactants are used up during the reaction
• What does a steep curve on the graph indicate?

  A high rate of reaction
• What are the axes labeled in the reaction graph?

  X-axis: time, Y-axis: volume of hydrogen
• How do you calculate the mean rate of reaction over three minutes?

  Divide hydrogen produced by three minutes
• What is the mean rate of reaction in the first three minutes?

  6.67 cm³ per second
• How do you find the rate of reaction at a specific time?

  Calculate the gradient of the curve at that point
• What is a tangent in relation to the curve?

  A straight line that touches the curve
• How is the gradient of the tangent calculated?

  Change in y divided by change in x
• If the change in volume of hydrogen is 600 and change in time is 170 seconds, what is the rate?

  3.53 cm³ per second
• What is the initial amount of magnesium used in the reaction graph?

  1.2 grams
• How do you find the rate of reaction at one minute using the magnesium graph?

  Draw a tangent and calculate the gradient
• What is the change in y when finding the rate at one minute?

  0.72 grams
• If the change in time is 100 seconds, what is the rate of magnesium reaction?

  0.0072 grams per second
• What should you do if your tangent is not perfect?

  Examiners allow a small range of values
• 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 interval.
• 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 to the curve at that point.
  3. Calculate the gradient of the tangent.
  4. Use the gradient formula: change in y / change in x.
• What are the characteristics of the magnesium remaining graph?

  • Starts at initial mass (1.2 grams)
  • Declines rapidly at first
  • Slows down as reaction progresses