Chemical Industry
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what is rate of reaction?
the change in the amount of reactants or products per unit time (normally per second)
What is the general equation for rate?
Rate = amount of reactant used/ product made / time
what is the rate constant - and what does it tell us
k units vary so have to work them out the bigger it is the faster the rate of reaction
what are orders of reaction?
• tells you how the reactant concentration affects the rate • rate is proportional to [A] • need order of reaction with respect to reactant • reaction also has an overall order which is the sum of the orders of the different reactants
how do you find the order w.r.t a reactant?
look at how each reactant affects the rate one by one if [A] changes and rate stays the same: 0 order w.r.t [A] if [A] doubles and rate double (proportional): 1st order w.r.t [A] if [A] double and the rate is 2^2 faster (triples is 3^2 faster): 2nd order w.r.t [A]
how does temperature affect the rate constant?
if you increase temperature you will increase the rate of reaction • more kinetic energy • particle speed up and are more likely to collide • have the right activation energy to react so greater proportion will have enough energy to react at a higher temperature the reaction will have a higher rate constant
What is half life?
The time taken for a reactant to halve in quantity.
What is the effect of adding a catalyst on the equilibrium constant?
None
What is the effect of increasing the temperature of a dynamic equilibrium on the position of equilibrium?
Will move it in the endothermic direction.
What is the effect of increasing the pressure of a dynamic equilibrium on the position of equilibrium?
It’ll move the position of equilibrium towards the side with the fewest moles of gas.
What is the effect of increasing the concentration of a reactant in a dynamic equilibrium on the position of equilibrium?
It will move to the right
What is the effect of increasing the pressure of a dynamic equilibrium on the equilibrium constant?
None
What is the effect of adding a catalyst on the position of equilibrium?
None
What is the effect of increasing the temperature of a dynamic equilibrium on the equilibrium constant?
Will increase if the forward reaction is endothermic, decrease if it’s exothermic.
What is the effect of increasing the concentration of a reactant in a dynamic equilibrium on the equilibrium constant?
None
How could you find the equilibrium concentration experimentally?
If it’s coloured, use colorimetry. If one of the sides contains an acid/alkali, use a pH meter. Then use the Kc equation to calculate its value.
How to follow the rate of reaction - experimental methods?
• pH measurement • gas volume • loss of mass • colour change • titration
Give an example of an initial rate experiment
Clock reactions
What are clock reactions?
measure how much time takes for a set amount of product to form changes as you vary concentrations of one of the reactants has an easily observable end point - a colour change - that tells you when desired product is formed the quicker the clock reaction finishes the faster the initial rate
what does the arrhenius equation link?
an equation that links the rate constant and activation enthalpy
arrhenius equation - as the activation energy gets bigger…..
…K gets smaller
arrhenius equation - a large Ea means….
…a slow rate not many particles have enough energy to react so only a few collisions will result in a reaction
arrhenius equation - as temperature rises….
…K increases
what is the rate determining step?
the slowest step in a multistep reaction the overall rate is determined by this