rates of reaction

• what is the rates of reactions?

  the speed that the reactants get turned into products
• what is an example of a slow rate of reaction?

  the rusting of iron, this could take years or decades.
• what is an example of a regular rate of reaction?

  the reaction between magnesium and an acid, this produces a gentle stream of hydrogen bubbles
• what is an example of a fast rate of reaction?

  fireworks, these take place in a fraction of a second
• how do we measure a rate of reaction?

  • how fast the reactants are being used up
  • or how fast the product are being formed
• the faster the rate...???

  the faster the reactants will be used up and turned into products
• what are the two equations we can use to measure the rate of reaction?

  rate of reaction = quantity of products formed(g)/time taken(s)

  or

  rate of reaction = quantity of reactants used(g)/time taken(s)
• what factors affect the rate of chemical reactions?

  • temperature
  • concentration/pressire
  • surface area
  • catalyst
• what is collision theory?

  in order for particles to react, they have to collide with each other with sufficient energy. we call this the activation energy, if they collide with less energy than this then nothing will happen, they will just bounce apart again
• what effect does the amount of energy the particles have have on the rate of reaction?

  • more energy they can transfer during the collision
  • more likely they are to pass the activation energy
• what effect does the frequency of collisions have on the rate of reaction?

  • even though not all collisions are successful, because the particles don't reach activation energy, the more often they collide the more successful collisions they will be overall
• what happens as the temperature of a reaction increases?

  • the particles gain more energy, this means they move faster.
  • as they're moving faster they will collide more frequently.
  • since they gain more energy the collisions will have more energy behind them
  • this means the particles are more likely to exceed activation energy
  • overall there will be a higher rate of successful collisions and a higher rate of reaction
• what happens as concentration/pressure is increased?

  • there will be more particles per unit of volume
  • this makes the collisions more frequent
  • this will increase the rate of reaction
• what does a higher surface area do?

  increase the rate of reaction
• which has the highest surface area out of a solid block, small chunks, and a powder of magnesium?

  the powder. this gives a much bigger space for reactions to take place, leading to an increase in the rate of reaction.
• what are catalysts?


  catalysts are substances that speed up a reaction without being used up in the reaction themselves
• what does a catalyst do to the activation energy on a reaction profile?

  it lowers the activation energy by providing an alternative, quicker reaction pathway. this means there will be a higher proportion of successful collisions.
• what are the most common catalysts?

  transition metals
• what do you divide to find the gradient?

  the length going up/the length across