Rates of Reaction

• What is the rate of a reaction?

  It is how quickly reactants are used up or products are produced.
• What is the equation for calculating the mean rate of reaction?

  change in quantity of product or reactant

  mean rate = ----------------------------------------

  time taken
• What is the unit for rate of reaction in a reaction involving a change in mass?

  g/s
• What is the unit for rate of reaction in a reaction involving a change in volume?

  cm^3/s
• How can you measure the rate of a reaction that produces a gas?

  Measure the change in mass using a balance.

  Measure volume of gas produced using a syringe or an upside down measuring cylinder.
• What is a precipitate?

  An insoluble solid in a solution.
• How can you measure the rate of a reaction that produces a precipitate?

  Measure how long it takes for a cross to disappear.
• What is the activation energy?

  It's the minimum amount of energy colliding particles have to have before a reaction will take place.
• What effect does increasing concentration have on the rate of reaction?

  Increase
• Why does increasing concentration have this effect?

  More reactant particles in the same volume lead to more frequent collisions.
• What does increasing pressure have on the rate of reaction?

  Increases.
• Why does increasing pressure have this effect?

  Less space between particles means more frequent collisions.
• What effect does increasing surface area have on the rate of reaction?

  Increases
• Why does increasing surface area have this effect?

  More reactant particles are exposed and able to collide, leading to more frequent collisions.
• What effect does increasing temperature have on the rate of reaction?

  Increases
• Why does increasing temperature have this effect?

  Particles move faster, leading to more frequent collisions - particles have the same activation energy so more collisions result in a reaction.
• What is a catalyst?

  It's a substance that increases the rate of a reaction but not used up in the reaction.
• How do catalysts increase the rate of a reaction?

  Lower the activation energy of the reaction, so more collisions result in a reaction.