9.1.1 Factors Affecting Reaction Rates

• What is the definition of reaction rate?

  How quickly a chemical reaction occurs
• Reaction rate is calculated as the change in concentration per unit time
• Common units for reaction rate include mol dm^-3 s^-1
• What does the collision theory state?

  Particles collide with sufficient energy
• Reactant particles must collide in a spatial arrangement called effective collisions
• Match the condition with its definition:

  Activation Energy ↔️ Minimum energy for reaction

  Effective Collision ↔️ Correct orientation for bond formation
• Arrange the key factors influencing reaction rates in order of importance:

  1️⃣ Temperature

  2️⃣ Concentration

  3️⃣ Surface Area

  4️⃣ Catalysts
• How does increasing temperature affect reaction rates?

  Increases kinetic energy of particles
• Higher concentration of reactants increases the frequency of collisions
• Catalysts increase reaction rates by lowering the activation energy
• Heating a reaction mixture to 60°C doubles the rate
• Doubling the concentration of reactants doubles the reaction rate
• How does surface area affect reaction rates?

  Increases contact and collisions
• Catalysts lower activation energy
• Arrange the key factors that influence reaction rates in order of their primary effect:

  1️⃣ Temperature increases kinetic energy

  2️⃣ Concentration increases collision frequency

  3️⃣ Surface area increases contact

  4️⃣ Catalysts lower activation energy
• What happens to collision frequency when temperature increases?

  Increases
• Higher concentration of reactants increases the frequency of collisions
• A greater surface area speeds up reactions involving solid reactants
• How do catalysts lower activation energy?

  Alternative reaction pathway
• Reaction rate is calculated as the change in concentration
• The unit for reaction rate can be mol dm^-3 s^-1
• What are the two conditions for a chemical reaction to occur according to collision theory?

  Energy and orientation
• Activation energy is the minimum energy required for a reaction to start
• An effective collision occurs when reactants align to form products
• Arrange the key factors that influence reaction rates in order of their primary effect:

  1️⃣ Temperature increases kinetic energy

  2️⃣ Concentration increases collision frequency

  3️⃣ Surface area increases contact

  4️⃣ Catalysts lower activation energy
• Increasing temperature increases the kinetic energy of reactant particles
• What is the Arrhenius equation?

  $k =$$Ae^{ - E_{a} / RT}$
• In the Arrhenius equation, $T$ represents temperature in Kelvin
• What does increasing temperature provide to reactant particles?

  More kinetic energy
• Higher temperatures increase the speed of particles, resulting in more frequent collisions.
• More particles possess energy greater than the activation energy
• What is the name of the equation that quantifies the relationship between temperature and reaction rate?

  Arrhenius equation
• Match the variables in the Arrhenius equation with their meanings:

  $k$ ↔️ Rate constant

  $A$ ↔️ Pre-exponential factor

  $E_{a}$ ↔️ Activation energy

  $R$ ↔️ Gas constant

  $T$ ↔️ Temperature in Kelvin
• What is the activation energy ($E_{a}$) in the Arrhenius equation?


  Minimum energy to react
• When the temperature increases from 25°C to 35°C, the rate constant doubles, indicating more particles overcome the activation energy barrier
• Steps to solve for $E_{a}$ using the Arrhenius equation when the rate constant doubles with a temperature increase:


  1️⃣ Write the Arrhenius equation at both temperatures

  2️⃣ Divide the equation at the higher temperature by the equation at the lower temperature

  3️⃣ Take the natural logarithm

  4️⃣ Solve for $E_{a}$
• What is the value of the gas constant ($R$) in the Arrhenius equation?


  $8.314 \, \text{J mol}^{ - 1} \text{K}^{ - 1}$
• Increasing temperature significantly increases the proportion of molecules with enough energy to react.
• According to collision theory, what happens to collision frequency when concentration increases?

  It increases
• Match the concentration level with its effect on collision frequency and reaction rate:

  Low concentration ↔️ Lower collision frequency, slower reaction rate

  High concentration ↔️ Higher collision frequency, faster reaction rate