Rates of Reaction

• What does the slope of the graph represent in a chemical reaction?

  The rate of reaction
• How does the slope of the graph change as the reaction proceeds?

  It becomes less steep over time
• Why does the reaction slow down as it progresses?

  Fewer reactant molecules are available
• What does a flat line on the graph indicate?

  The reaction has stopped
• In what unit is the quantity of product measured if it is a gas?

  Centimeters cubed
• How can the mean rate of a reaction be calculated?

  Quantity of product divided by time taken
• If 20 grams of product is formed in 40 seconds, what is the mean rate of reaction?

  0.5 grams per second
• How do you calculate the mean rate of reaction from the quantity of reactant used?

  Quantity of reactant divided by time taken
• What is the mean rate of reaction if 30 grams of reactant is used in 10 seconds?

  3 grams per second
• If 150 grams of reactant is used in 75 seconds, what is the mean rate of reaction?

  2 grams per second
• What are the key points to remember about the graphs of chemical reactions?

  • Slope indicates rate of reaction
  • Steeper slope means faster reaction
  • Flat line means reaction has stopped
  • Quantity of product can be in grams or cm³
• What is the formula for calculating the mean rate of reaction?

  Mean rate of reaction =

  • Quantity of product formed / Time taken
  • Quantity of reactant used / Time taken
• How can the slope of the tangent be used in this context?

  As a measure of the rate of reaction
• How do scientists measure the rate of reaction at a specific point on the curve?

  By drawing a tangent that touches the curve
• What is the straight line that touches the curve called?

  Tangent
• What does a steeper slope of the tangent indicate about the reaction?

  The reaction is faster at that point
• What is the purpose of constructing a triangle using the tangent?

  To measure the rate of reaction
• How do you find the vertical side of the triangle from the graph?

  By reading values from the y-axis
• How do you find the horizontal side of the triangle from the graph?

  By reading values from the x-axis
• How do you calculate the rate of reaction using the triangle?

  Divide Y by X
• What are the key steps to measure the rate of reaction using a tangent?

  1. Draw a tangent at the point of interest.
  2. Construct a triangle using the tangent.
  3. Measure the lengths of the vertical and horizontal sides.
  4. Calculate the rate by dividing the vertical side by the horizontal side.
• What is the significance of the slope of the tangent in reaction rate analysis?

  • Indicates the rate of reaction at a specific point
  • Helps in calculating the reaction rate
• What is the initial behavior of chemical reactions over time?

  They are rapid initially, then slow down
• What does collision theory state?

  Reactions occur when particles collide with energy
• How does the frequency of successful collisions affect reaction rates?

  Higher frequency increases the reaction rate
• Why do reactions slow down over time?

  Reactant molecules are running out
• What happens when all reactant molecules are used up?

  The reaction stops completely
• How does concentration affect the rate of reaction?

  • Higher concentration increases collision frequency
  • More collisions lead to a faster reaction rate
  • Rate is proportional to concentration
• What happens to the number of collisions per second when concentration doubles?

  It also doubles
• How does gas pressure relate to reaction rates?

  Higher pressure increases collision frequency
• What differences are observed in product quantity with varying concentrations?

  • Higher concentration yields more product
  • Reaction rate is faster with higher concentration
  • Steeper product quantity line on graph
• How does temperature affect the rate of chemical reactions?

  Higher temperature increases reaction rates
• What is a catalyst?

  A substance that speeds up reactions
• What defines a successful collision in chemistry?

  Collisions with sufficient energy to react
• What is reaction equilibrium?

  When reactants and products are balanced
• How does surface area influence reaction rates?

  Larger surface area increases reaction rates
• What is a hypothesis in science?

  A testable proposal explaining observations
• What reaction is used in the disappearing cross experiment?

  Sodium thiosulfate with hydrochloric acid
• What product is formed in the disappearing cross reaction?

  Solid sulfur
• What is turbidity in a solution?

  Cloudiness of the solution