Kinetics Chemistry urgent

In GCSES the rate of reaction is product formed/reactant used over time however in AS Chemistry it says rate of reaction is change in conc. over time. I'm so confused someone please help me

Reply 1

Lissy14

Original post by Love123443

In GCSES the rate of reaction is product formed/reactant used over time however in AS Chemistry it says rate of reaction is change in conc. over time. I'm so confused someone please help me

Essentially they are the same thing. Let's just look at it in terms of reactant used.

The 'GCSE' version: rate = reactant used divided by time

The 'A level' version: this uses concentration. Concentration is defined as 'amount of reactant in liquid'. Therefore 'change in concentration' is the same as 'change in amount of reactant in the liquid'.
Rate = change in concentration divided by time = change in amount of reactant in the liquid divided by time

So if you compare the 'GCSE' and 'A level' versions you can see that they are really the same.
This is because 'change in amount of reactant in the liquid (aka Change in concentration)' is the same as 'reactant used'.

Sorry, I'm not sure I explained that very well - let me know if you need me to try again.