Rate of Reaction and Rate Laws
The rate law expresses reaction rate as a function of concentrations, with orders determined experimentally rather than from stoichiometry.
What is Rate of Reaction and Rate Laws?
The rate law expresses reaction rate as a function of concentrations, with orders determined experimentally rather than from stoichiometry.
Key formula / rule: Order is determined experimentally and may be fractional or zero.
Key points
- Derive the integrated rate law for a first-order reaction.
- Compute reaction order from experimental rate data.
Common exam trap
Reading reaction order from the balanced equation coefficients.
Definitions
- Term
Rate of Reaction and Rate Laws
- Meaning
The rate law expresses reaction rate as a function of concentrations, with orders determined experimentally rather than from stoichiometry.
- Term
Rate of Reaction and Rate Laws — explanation
- Meaning
Order and molecularity are distinct: order is empirical and can be fractional, while molecularity counts species in an elementary step. This distinction is examined every year.
Learning objectives
Derive the integrated rate law for a first-order reaction.
Compute reaction order from experimental rate data.
Formulae
- Key point
Order is determined experimentally and may be fractional or zero.
- Key point
Rate constant units depend on the overall order.
- Key point
For a first-order reaction, half-life is independent of initial concentration.
Common mistakes
Reading reaction order from the balanced equation coefficients.
Using first-order half-life independence for other orders.
Keywords
Rate
Reaction
Rate
Laws
Practice preview
What are the standard units for the rate of a chemical reaction?…
easy
If the rate law for a reaction is given as Rate = k[A]²[B]¹, what is the overall order of the reaction?…
medium
For a reaction A + B -> Products, the rate law is Rate = k[A]²[B]¹. If the concentration of A is doubled and the concentration of B is halved, what will be the effect on the reaction rate?…
medium