1.9 Rate Equations

It tells you how much the concentration of a reactant affects the rate

The power to which a concentration is raised in the rate equation

The sum of the individual orders in the rate equation

rate = k[A][B] With powers on the concentrations depending on the order K=rate constant

It doesn’t appear in the rate equation

Continuous monitoring Initial rate method

Graph - concentration v time Then draw tangents of your curve and workout the gradients of each for the rate of reaction (Y/X) Graph - rate of reaction v concentration Draw lines from line of best fit to check (at least two)

First - the rate is proportional to the concentration Second - the rate is proportional to the square of the concentration Zero - the rate doesn’t depend on the concentration = no effect (defo the one in excess)

From a data table you look at 2 experiments Find one where the other reactant concentrations (B) are the same and (A) is different Look at the difference of A’s between the experiments then look at the difference in the initial rate and work out the difference Determine the order depending on if they both multiply by the same, the square or no effect

Create a rate equation with the orders determined from the table Then substitute and rearrange the rate equation to work out k (the rate constant)

Mol dm^-3 s^-1

The slowest step in a chemical reaction

You look at the rate equation and it is the step that has the same proportions of reactants rate = k[A]^2[B] RDS = (eg) B + 2A -> C Be careful as some may be in disguise from previous steps

Plot 1/T against ln k (log K) (Might have to work out k from rearranging the rate equation with values?) Workout gradient from plotted line y/x Large (minus) number Multiply this number by 8.31 Then divide by 1000 to put it in KJ mol-1

If you do the axis to x10^-3 make sure you multiply the number you use in the gradient calculation by x10^-3