How and why does temperature affect rate of reaction?
- higher temp = faster RoR
* KE of particles is + ∴ move around more ∴ collide more freq ∴ more successful collisions per sec
How do you test the affect of temperature on RoR?
- get 2x beakers and measure out 50ml sodium thiosulfate and 5ml of HCl
- keep the sodium thiosulfate in a baine Marie until a certain temp, e.g. 40°C
- once it has reached this temp, quickly add to the HCl in a beaker on top of a paper with a cross on it.
- time until you can no longer see cross as too cloudy
How and why does concentration affect RoR?
- higher conce= faster RoR
* if conc +, more particles in the are to react ∴ greater freq reactions ∴ more success reactions per sec
How do you test the affect of concentration on RoR?
- mix HCl w water in different ratios i.e. 20ml to 0ml, 8ml to 12ml 12ml to 8ml 4 ml to 6ml, to achieve different concs
- react the solution w 2g calcium carbonate chips in a test tube w a bung reading to a gas syringe at the top
- measure volume of CO2 formed in 30secs at the different concs
How and why does surface area affect RoR?
- higher SA = faster RoR
- increases num particles that are exposed and available to react ∴ collisions more freq ∴ faster num of succ collisions per sec
How do you test the affect of SA on RoR?
- take a 4cm long piece of rhubarb and weight it
- place in 30cm3 of potassium manganate
- time how long it takes the potassium manganate to go colourless
- repeat w same size + mass of rhubarb but each time cut it lengthways in half one more time, e.g. 2, 4, 8 pieces ∴ having different SAS, and see how long each of this takes to turn colourless
How and why does pressure affect rate of reaction?
- high pres= faster RoR
- pres means forcing gas particles closer together ∴ more freq collisions ∴ faster RoR
- only in gas reactions
How and why does a catalyst affect rate of reaction?
- speeds it up
- provides an alternate route for reaction w lower activation energy ∴ less energy needed to start reaction
- is not used up during the reaction
How do you test the affect of catalysts on RoR?
- hydrogen peroxide does not normally decompose. If you add managnese dioxide it will decompose to water and oxygen (formations of O₂ experiment)
- manganese dioxide remains unaltered (weigh before +after) ∴ catalyst
What is activation energy?
Min amount of energy particles must colllide w for reaction to happen
What does an RoR graph look like?
- time of reaction on x, amount of prod of y, ∴ rate of reaction is the grad
- steep at start as high number of particles reacting w high frequency
- becomes more shallow as the number of reactions has decreased, as they were used to form products ∴ lower RoR
- eventually stops when all reactants used up
How do you calculate RoR?
RoR = amount o reactant used / time RoR = amount of product made / time