https://padlet.com/hol_cjones/e1cpjyfpe51v Made with the strength to succeed en-us 2019-01-30 12:12:16 UTC 2026-01-03 09:17:52 UTC hello@padlet.com https://padlet-assets.s3.amazonaws.com/icons/Soccerball.png 317683 https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795135 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.]]> 2019-01-30 12:12:24 UTC https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795135 317683 https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795136 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

]]> 2019-01-30 12:12:24 UTC https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795136 317683 https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795137 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. ]]> 2019-01-30 12:12:24 UTC https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795137 317683 https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795138 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.]]> 2019-01-30 12:12:24 UTC https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795138 317683 https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795139 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.]]> 2019-01-30 12:12:24 UTC https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795139 317683 https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795140 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]]> 2019-01-30 12:12:24 UTC https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795140 317683 https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795141 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.]]> 2019-01-30 12:12:24 UTC https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795141 317683 https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795142 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]]> 2019-01-30 12:12:24 UTC https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795142 317683 https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795143 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

]]> 2019-01-30 12:12:24 UTC https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795143 317683 https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795144 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.]]> 2019-01-30 12:12:24 UTC https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795144 317683 https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795145 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:]]> 2019-01-30 12:12:24 UTC https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795145 317683 https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795146 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.]]> 2019-01-30 12:12:24 UTC https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795146 hol_cjones https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795147 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. ]]> 2019-01-30 12:12:24 UTC https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795147 hol_cjones https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795148 The rate of the slowest step limits the rate of the overall reaction.]]> 2019-01-30 12:12:24 UTC https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795148 317683 https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795150

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 

]]> 2019-01-30 12:12:24 UTC https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795150 317683 https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795151 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]]> 2019-01-30 12:12:24 UTC https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795151 hol_cjones https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795152 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
E_a 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. ]]> 2019-01-30 12:12:24 UTC https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795152 hol_cjones https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795153 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.]]> 2019-01-30 12:12:24 UTC https://padlet.com/hol_cjones/e1cpjyfpe51v/wish/325795153