C6- ROCC

• What is the term for how quickly a reaction happens?

  Rate of reaction
• How is the rate of reaction defined?

  Change in quantity divided by time
• What can the quantity in a rate of reaction refer to?

  Mass or volume of gas produced
• What does the mean rate of reaction indicate?

  Average rate over the measurement period
• Describe an experiment to measure the rate of reaction using hydrochloric acid and sodium thiosulfate.

  • Use a conical flask with a cross beneath
  • Observe cloudiness as the reaction occurs
  • Stop timing when the cross is no longer visible
  • Repeat at different temperatures
• What does increased turbidity indicate in the reaction?

  Formation of a cloudy solution
• What is the purpose of a gas syringe in measuring reaction rates?

  To measure volume of gas produced
• How is a graph of gas volume against time typically shaped?

  Starts steep, then levels out
• What does the leveling out of the graph indicate?

  The reaction has completed
• How can you find the rate of reaction at any time on a graph?

  Draw a tangent at that point
• What is the formula to calculate the rate of reaction using a tangent?

  Change in quantity divided by time
• What factors can increase the rate of a reaction?

  • Increasing concentration of reactants
  • Increasing pressure of gas reactants
  • Increasing surface area of solid reactants
• Why does increasing concentration affect reaction rate?

  Particles collide more frequently
• How does increasing temperature affect reaction rate?

  Particles move more quickly and collide with energy
• What role does a catalyst play in a reaction?

  Reduces activation energy needed
• What is a characteristic of a catalyst?

  Not used up in the reaction
• What is a reversible reaction?

  • Products can revert to reactants
  • Example: Haber process (N2 + H2 ⇌ NH3)
  • Equilibrium reached in a closed system
• What happens at equilibrium in a closed system?

  Rates of forward and reverse reactions equal
• What does Le Chatelier's principle state?

  System adjusts to counteract changes
• How does increasing pressure affect a reaction with more moles on the left side?

  Favors the forward reaction
• What happens when the concentration of reactants is decreased?

  Equilibrium shifts towards the side with fewer moles
• How does temperature affect endothermic and exothermic reactions?

  Higher temperature favors endothermic reactions
• What is the relationship between forward and reverse reactions in reversible reactions?

  If forward is exothermic, reverse is endothermic
• What is the significance of the Haber process?

  • Produces ammonia from nitrogen and hydrogen
  • Demonstrates reversible reactions
  • Important for fertilizer production