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Catalysts increase rates of reactions by providing alternative routes with lower activation energies.
This doesn’t affect the concentrations in rate equation, therefore the rate constant is changed.
As the route of reaction changes, the value of A (the frequency) also changes. - The combination of both will lea to a significant increase in rate of reaction.

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Can be found by rearranging Arrhenius equation if we have information about frequency factor (A)
Easier to find info regarding the rate constant at different
temperatures.- This will allows us to find frequency factor and activation energy.
Rearranged to give: ln k = ln A - E a/RT
Can be used to plot a straight line graph of k against 1/T.
The intercept gives ln A and gradient is -E a/RT
k is the log of the rate constant
1/T uses the temperature in Kelvin
Gradient needs to be multiplied by -8.314 J K-1 mol-1 to find a value for the activation energy (units = J mol⁻¹) (to convert to kJ mol-1 divide answer by 1000)
To find the value fo A, use e(intercept value). Units are the same as the rate constant

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Collision Theory: For a reaction to occur, reacting particles must collide and these particles must have sufficient energy for reaction (activation energy)
The rate equation tells us how many particles must collide in the rate-determining step.

In a first order reaction, there is only one particle in the rate determining step

In a second order reaction, two particles must collide

In a third order reaction, 3 particles must collide

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1. look @ information to find 2 experiments that differ in conc. of 1
2. if doubling the reactant conc. has no affect, the order is zero
3. if doubling the reactant conc. doubles the rate of the reaction, order is one
4. if doubling the reactant conc. increases the rate by a factor of 4, the order is two
5. repeat this process for each reactant, to find the order with respect to each one
6. the order of the Rea lion is the sum of these orders

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Rate equations can only be found experimentally, by studying the effects of changing the concentration of each individual reactant. There is no way of obtaining this rate equation from the overall equation of the reaction.

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rate is moldm⁻³s-1
0th order units of K = moldm⁻³s⁻¹
1st order units of K = s⁻¹
2nd order units of K = mol⁻¹dm³s⁻¹

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Rate - rate of the change of conc. or of the amount of a particular reactant or product.
Rate constant - a constant in the equation, constant for a given reaction at a particular temp, not affected by the changing conc. Not constant if temp changes.
Order of reaction - with respect to a particular reactant is the power to which the conc is raised in then rate equations.
Overall order is the sum of the 2 powers.
0 - zeroth order
1 - first order
2 - second order
3 - third order

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Generally -
A + B --> products
The rate equation is:
Rate = k [A]m[B]n
k is the rate constant.
m is the order of reaction with respect to A.
n is the order of reaction with respect to B.

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The rate of a reaction in solution depends on the conc of the reactants. When the conc of 1 reactant [A] is doubled, the rate may:

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If a reaction uses a heterogeneous catalyst the sampling can happen without quenching. Removing a sample of gas or liquid takes it from the catalyst so the rate is immediately reduced.
If a reaction uses a homogeneous catalyst then taking a sample also takes a sample of the catalyst, so the reaction continues. Quenching is needed in this case & can use cooling & diluting. Can also be quenched by destroying the catalyst, e.g an acid catalyst can be neutralised with alkali.

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In the rate equation, temperature doesn’t affect the concentrations of each substance therefore it’s the rate constant that’s affected.
k=Ae-E A(RT)
k is the rate constant
A is the frequency of collisions between particles.
e is a button on the calculator
Ea is the activation energy (J mol⁻¹)
R is the gas constant, 8.314 J K-1 mol-1
T is the temperature in Kelvin.
This is considered to show the collisions that have energy levels higher than the activation energy.

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Used for a large range of reactions

Labour & time intensive as each sample must be analysed individually

sampling only appropriate with a homogeneous reaction mixture e.g all in solution. If not the sample may not be representative of then mixture

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Increasing the temperature causes the rate to increase.
This is because when a temperature increases, the number of particles with energy higher than the activation energy increases. This means that there will be more successful collisions.

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The rate of the slowest step limits the rate of the overall reaction.

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A description of the steps that occur during a chemical reaction by which reactants become products. Each step will occur at a different rate with its own rate equation.

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The rate is calculated using the equation:
rate = change in conc. ÷ time taken
The average rate over the time period. The conc. changes as the reaction progresses so it's likely that the rate will also change, with the rate decreasing as the conc. of reactants decrease. Finding the initial rate, should be plotted on a graph & a tangent drawn to the curve at time=0.
Rate can be measured at different times by plotting a tangent at different places on the curve.

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Where small amounts of each reaction mixture is removed at regular intervals(sampling) and immediately placed into iced water. This cools & dilutes the reaction mixture, slowing the reaction down & stopping it. This is quenching.
Samples must be analysed appropriately, titration is common. Each sample analysed individually to get information on the progression of the reaction.

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First we need to work out how much of a reactant has been used up or how much of a product has been produced in a given time. E.g the mass of reactants, volume/pressure of a gas, colour absorptions.