# Kinetics

Syllabus notes from unit 4 AQA kinetics. A2 level

HideShow resource information

## Rate equation

Rate = k [A]x [B]Y

• rate = mol dm-3 s-1 = change of conc per unit time
• k = rate constant
• A, B are reactants
• [ ] = conc = mol dm-3
• Overall order of reaction = X +Y
1 of 4

## Deriving rate equation from experimental data

Methods:

• collecting gas evolved
• colorimetry
• titration

If reactant conc doubles and rate doubles = order 1

If reactant conc doubles and rate quadroubles = order 2

If rate independent to conc = order 0

2 of 4

## changes of temp on K

K

• different for every reaction
• varies with temp
• if all concentrations of all species in the rate equation are 1 mol dm-3, then the rate equation is equal to the value of k
• units obtained by cancelling
• for every 10k rise in temp reaction rate doubles
• allows comparisons of speeds of different reactions at a given temp
• larger the value of k, the faster the reaction
• values of k increases with temp.
3 of 4

## rate determining step

• slowest step of reaction
• controls overall rate
• any step that occurs afterwards will not effect rate.
4 of 4