RATE OF REACTION

• how do you calculate the mean rate of reaction?

  mean rate of reaction = quantity of reactant/product formed / time taken
• which factors affect the rates of chemical reactions?

  - concentrations of reactants in solution

  - pressure of reacting gases

  - surface area of solid reactants

  - temperature

  - presence of catalysts
• what is collision theory?

  the rate of a chemical reaction depends on collision frequency and energy transferred during a collision
• how does an increase of temperature increase the rate of reaction?

  - increased temperature makes all particles move faster

  - particles collide more frequently

  - the faster they move, the more energy they transfer
• how does an increase of concentration or pressure increase the rate?

  - if pressure or concentration is increased there are more particles in a certain volume

  - this makes collisions more frequent
• how does increasing the surface area increase the rate?

  - if one of the reactants is a solid, then breaking it into smaller pieces increases its surface area to volume ratio

  - so particles around the reactant will have more area to collide with
• what is a catalyst?


  a substance that speeds up a reaction, without being used up in the reaction itself
• how does a catalyst increase the rate of reaction?

  they lower the activation energy needed by providing an alternative reaction pathway
• which conditions does the position of equilibrium depend on?

  - concentration

  - temperature

  - pressure
• what is le chatelier's principle?

  the idea that if you change the conditions of a reversible reaction at equilibrium, the system will try to counteract that change
• what happens when you increase the concentration of the reactants?

  more products will be formed
• what happens when you decrease the concentration of the products?

  more reactants will be formed
• what happens when you increase the temperature of a system at equilibrium?

  equilibrium will move in the endothermic reaction
• what happens when you decrease the temperature of a system at equilibrium?

  equilibrium will move in the exothermic reaction
• what happens when you increase the pressure of gaseous reactions at equilibrium?

  equilibrium will move in the direction where there are fewer molecules of gas
• what happens when you decrease the pressure of gaseous reactions at equilibrium?

  equilibrium will move in the direction where there are more molecules of gas