Rates of reaction

formula for calculating rates

change in amount of reactant or product / time

3 ways to measure rates …

1. volume of gas produced

2. mass lost

3. colour change - stop clock when cross disappears

rate of reaction is determined by

the number of successful collisions per second

what happens at start, middle, end. what is the gradient?

Start - steep gradient, lots of gas, fast rate

middle - graph gets less steep, less gas produced, slower rate

end - graph flat, no gas being produced, reaction has finished, limiting reagent used up (link to q)

gradient = rate

where it ends = amount of product formed

how does increasing temp affect rate of reaction

• particles have more energy

• more particles have energy greater than activation energy

• more successful collisions per second

• faster reaction

how does increasing surface area affect rate

• more particles are exposed for collisions

• more successful collisions per second

• faster reaction

how does conc or pressure affect the rate?

• more particles are squeezed into the same volume

  • or same number of particles, smaller volume

• more successful collisions per second

• faster reaction

how does catalyst affect rate of reaction

• a catalyst speeds up a reaction without being used up

• it provides an alternative route with a lower activation energy