(6) 20 questions

• what is the formula for a mean rate of reaction in terms of reactants

  quantity of reactant used up / time taken
• what is the formula for a mean rate of reaction in terms of products


  quantity of product formed / time taken
• what are the two possible units for rate of reactions

  g/s or cm3/s
• how could you calculate the rate of reaction at a particular time from a graph

  draw a tangent to the curve and calculate the gradient
• what is collision theory


  the theory that chemical reactions only occur when particles collide with sufficient energy
• which five factors affect the rate of reaction

  temp, surface area, concentration, pressure, catalyst
• state the effect of increasing the surface area on the rate of reaction

  increases rate
• what is the name given to the minimum amount of energy that reacting particles must have to reaction

  activation energy
• explain why increasing the concentration increases the rate of reaction

  there are more particles of reactant in solution, therefore there are more frequent collisions between reactant particles
• what is a catalyst


  a substance that increases the rate of reaction without being used up or altered in the process
• how does a catalyst work

  it offers an alternative route for the reaction with a lower activition energy
• explain why decreasing the temp of a reaction would decrease the rate of a reaction

  reactant particles have less kinetic energy so their speed decreases = less frequent collisions + fewer particles have the required activation energy so fewer successful collisions form a reaction
• what is a reversible reaction


  a reaction that can go both in the forwards and backwards
• when is a system in dynamic equillbrium

  when the rate of the forward reaction is equal to the rate of the backward reaction
• is the amount of reactant changing at equillbrium

  no
• what is Le Chateliers principle

  when the conditions of a reaction at equilibrium are changed, it will shift the position of equilibrium to counteract that change
• a reaction is exothermic in the forward direction. what will occur if the temp is increased

  equilibrium will shift to the left, the backwards reaction will increase as it is endothermic and this will decrease the temp
• a reaction is at equilibrium when some of the product is removed. what will occur


  equilibrium will shift to the right, the forward reaction will increase making more product to replace what was removed
• how does increasing the pressure affect equilibrium

  it will shift equilibrium to the side with fewer moles of gas