rate equations
- Created by: Lucybarrow444
- Created on: 07-10-19 12:05
what is the rate equation
Rate = k[A]m [B]n
where m and n are the orders of reaction with respect to the reactants A and B. K is the rate constant
orderds m and n are restricted to values 0,1 and 2
what is the Arrhenius equation and what does it sh
k = Ae–Ea/RT
the rate constant k varies with temperature as shown by the equation
A is the Arrhenius constant, Ea is activation energy, T is the temperature in kelvins, R is the gas constant ( be given when required), and e is a constant (on a calculator).
explain the effect of changes in temp on the rate
the higher the temperature the
- more kinetic energy each particle has
- therefore a greater proportion of particles have energy greater than or equal to the activation energy
- therefore there is a greater frequency of succesful collision
if the temperature gets 10 kelvin higher, the rate is approximately double
how would you use the Arrhenius Equation as a grap
rearrange it to
ln k = –Ea /RT + ln A
where y= ln k, x= 1/T, m= -Ea/RT and C=Ln A
define the rate of reaction
the change in concentration per unit of time
define the activation energy
the minimum energy required for a reaction to occur
what is a catalyst and how does it work
it is a substance which increases the rate of reaction without being used up by providing an alternate reaction route with a lower activation energy.
what do the different orders mean
- zero-order means the changing concentration of the reactant has no effect on the rate of reaction
- the first order is directly proportional to the concentration
- the second-order is proportional to the square of the change in concentration e.g. doubling the concentration causes the rate to increase by 4 (2 squared)
how do you determine the orders of reaction using
when a rate vs conc graph is a horizontal line it means the reagent is zero order
when a rate vs conc graph is a straight line it means the reagent is 1st order
when a rate vs conc graph is a line curving up it means the reagent is 2nd order
how do you determine the rate determining step in
the species in the rate determining step must match the species in the rate equation
how do you find the overall order of reaction
by adding up all the orders in the equation
define the terms order of reaction and rate consta
the order of reaction with respect to a particular reactant is the power to which the concentration of this reactant is raised in the rate equation
the rate constant is the proportionality constant which links the rate of reaction to the concentrations in the rate equations
what are the rate units for the overall order of r
1- s-1
2- mol-1dm3s-1
3- mol-2dm6s-1
4- mol-3dm9s-1
4- mol-4dm12s-1
why do many chemical reactions start off with fast
- initially there is a high concentraion of reactants so a large frequency of succesful collision
- as the reactnats start to get used up succesful collision becomes less frequent
- once one or more reactants are used up there can be zero succesful collisions
how to draw conc x time graph of A + 2B--> C
- As A and B are both reactants their concentrations go down and as C is a product its concentration goes up
- B starts off twice as high as A because in the equation it shows that twice as much of B is required for the reaction
- all three graphs become horizontal at a certain time because no concentrations change which indicates the reaction has finished or is at equilibrium.
to meausre the initial rate a tangent is drawn at t=0 and to find the rate of reaction at a given time you use a tangent.
Related discussions on The Student Room
- A2 Rate equation Chemistry Question »
- rate Equation and Temperature »
- 2Al(s) Fe2O3(s) → Al2O3(s) 2Fe(s), struggling with this question »
- Orders of reaction »
- Rate equation question »
- Biology rate of reaction question »
- Reaction Rates »
- IAL Chemistry - Unit 4 EXAM DISCUSSION »
- Chemistry IA. »
- An Oscillating Capacitor Isaac physics »
Comments
No comments have yet been made