Finding Reaction Rates from Graphs

• What is the focus of the study material?

  Finding reaction rates from graphs
• What does the study material suggest about interpreting graphs?

  It shows how to calculate reaction rates
• How can you calculate the mean reaction rate from a graph?

  By finding the overall change in y-value
• What does a reaction graph show on the axes?

  • y-axis: amount of product formed or reactant used
  • x-axis: time
• How do you find the mean rate for the whole reaction?

  Calculate overall change in y-value divided by total time
• What is the formula for mean reaction rate?

  Mean rate = change in y / change in x
• If the change in volume is $19 \text{ cm}^3$ and the change in time is $20 \text{ s}$, what is the mean reaction rate?


  $0.95 \text{ cm}^3/s$
• What should you remember when finding the mean rate for the whole reaction?

  The reaction finishes at zero on the graph
• How do you find the reaction rate at a particular point on a graph?

  • Draw a tangent to the curve at that point
  • Calculate the gradient (slope) of the tangent
• What is the easiest way to find the gradient of a curve?

  Draw a tangent line at the point of interest
• What does the tangent line touch on the curve?

  It touches the curve at one point
• How do you work out the gradient of the tangent?

  Calculate the rise over run of the tangent
• What does the graph show about the mass of reactant used?

  • Mass is measured at regular intervals
  • It indicates the progress of the chemical reaction
• What is the reaction rate at 3 minutes if the mass of reactant is measured?

  It is determined by the graph's slope
• What should you do to find the reaction rate at a specific time?

  Position a ruler on the graph at that time
• What does the graph below show?

  The mass of reactant over time
• What is being measured at regular intervals during a chemical reaction?

  The mass of reactant used
• What is the rate of reaction at 3 minutes?

  0.27 g/min
• How do you determine the rate of reaction from a graph?

  1. Position a ruler on the graph at the point of interest.
  2. Adjust the ruler until the space between the ruler and curve is equal on both sides.
  3. Draw a line along the ruler to create a tangent.
  4. Pick two points on the tangent line to calculate the gradient.
  5. Use the formula:

  $\text{Gradient} =$$\frac{\text{change in } y}{\text{change in } x}$
• How do you calculate the gradient of the tangent?

  Change in y divided by change in x
• What is the formula to find the rate of reaction using two points?

  $\text{Rate} =$$\frac{(2.2 - 1.4)}{(5.0 - 2.0)}$
• What is the calculated rate of reaction at 3 minutes?

  0.27 g/min
• What is the significance of the rate of reaction?

  • Indicates how fast reactants are converted to products
  • Important for understanding reaction kinetics
  • Helps in optimizing reaction conditions
• What was added to the conical flask in the experiment?

  Magnesium powder
• What gas was produced during the reaction?

  Hydrogen gas
• What was the volume of gas released at 10 seconds?

  7 cm³
• What was the volume of gas released at 40 seconds?

  40 cm³
• What are the steps to plot results on a graph?

  1. Record the volume of gas at each time interval.
  2. Plot the volume on the y-axis and time on the x-axis.
  3. Draw a line of best fit through the points.
• What is the purpose of drawing a line of best fit?

  To visualize the trend in data
• What is the rate of reaction at 25 seconds?

  0.25 g/min
• What is the final rate of reaction calculated?

  0.27 g/min
• What factors can affect the rate of a chemical reaction?

  • Concentration of reactants
  • Temperature of the reaction
  • Surface area of solid reactants
  • Presence of catalysts
• What is the chemical change being studied?

  The reaction of magnesium with dilute H₂SO₄
• Why is it important to practice calculating reaction rates?

  To improve understanding of chemical kinetics
• What is the main takeaway from the experiment?

  Understanding how to calculate reaction rates
• What is the relationship between the rate of reaction and time?

  • Rate of reaction decreases as time increases
  • Rate can be calculated at specific time intervals
  • Graphs can illustrate this relationship