Rates of reaction
, Orders of reaction
Every reaction has a rate.
Rate=quantity reacted/produced Rate=change in concentration
time change in time
Changing the concentration often changes the rate of
reaction. The rate of reaction is proportional to the
concentration of a particular reactant raised to a power.
For each reactant, the power is the order of the reactant
Zero order- when the concentration of the reactant has no
effect on the rate. [A]0=1
First order- a reaction is first order if any change in
concentration gives the same change to the rate-[A]1=[A]
Second order- a reaction is second order when a change in
concentration changes the rate by the square of the change.
[A]2
, The rate equation
Rate=k[A]m[B]n
The rate equation gives the mathematical relationship
between the concentrations of reactants & the reaction rate.
The rate constant, K, is the proportionality constant. It is the
number that mathematically converts between the rate of
reaction and concentration and orders. K increases as temp
increases & as surface area of solid increases.
The overall order= sum of all orders (number of moles have no effect on order)
Overall order for k[A]m[B]n = m+n
The units of the rate constant can be determined by:
1. Rearranging the equation to make k the subject
2. Substitute units into the expression for k
3. Cancel common units & show the final units on a single line
e.g. rate= k[A]2[B]1
K= rate units of k= moldm-3s-1 =dm6mol-2s-1
[A]2[B]1 (moldm-3)2(moldm-3)
, Orders of reaction
Every reaction has a rate.
Rate=quantity reacted/produced Rate=change in concentration
time change in time
Changing the concentration often changes the rate of
reaction. The rate of reaction is proportional to the
concentration of a particular reactant raised to a power.
For each reactant, the power is the order of the reactant
Zero order- when the concentration of the reactant has no
effect on the rate. [A]0=1
First order- a reaction is first order if any change in
concentration gives the same change to the rate-[A]1=[A]
Second order- a reaction is second order when a change in
concentration changes the rate by the square of the change.
[A]2
, The rate equation
Rate=k[A]m[B]n
The rate equation gives the mathematical relationship
between the concentrations of reactants & the reaction rate.
The rate constant, K, is the proportionality constant. It is the
number that mathematically converts between the rate of
reaction and concentration and orders. K increases as temp
increases & as surface area of solid increases.
The overall order= sum of all orders (number of moles have no effect on order)
Overall order for k[A]m[B]n = m+n
The units of the rate constant can be determined by:
1. Rearranging the equation to make k the subject
2. Substitute units into the expression for k
3. Cancel common units & show the final units on a single line
e.g. rate= k[A]2[B]1
K= rate units of k= moldm-3s-1 =dm6mol-2s-1
[A]2[B]1 (moldm-3)2(moldm-3)
