rates reactions effects and that Flashcards
two ways to work out rate of reaction
amount of product used and made
steeper the gradient..
faster rate of reaction
how to find a tanegnt
draw a straight line coming off a point in the graph which is like a straight reflction of the crve idk. then connect the line to make a right angle triangle and measure the lengths of the x and y side. then divide y by x to get the rate of reaction
why do we need tangents
to find the rate of a reaction ina specific point when the graph is curving
req practical 5 (cross one)
put 10cm of both sodium thiosulpahte and hydrochloric acid into a concial flask and swirl until mixed, start stopwatch. put it also ontop of a black x. someone stares at the mixture until theyre unable to see the x and they record the time, this repeats with dif concentrations
issues with req practical 5
everyones eyes are different sp it has to be the same -person each time
mean RoR
= quantity/time
increased sa…
increased rate of reaction because more pieces of the substance are surrounded by solution so can react
increased concentration…
increased RoR
repoucable experiemnt
you get the same sollution to ypur hypothesis regardless of if you change the apparatus, person working on it etc
why does raising the temp increase RoR
gain energy which makes them more energetic heightening chances of collisions and reactions
collisions are more frequent as the speed is increased
things that are proportional to rate
temp
concentration
surface area
catalyts
pros of catalysts
are not used up in a reaction, cheaoper because heat isnt needed for reactions, lowers the activation energy so theres less energy needed to react and more sucessful collisions
how do catalysts help the enviroment
can be reused, work instead of increasing temps which often means fossil fuels burnt. stops co2 entering the atmosphere
what is collision theory
the fact that particles need enough energy to collide to cause a reaction to take place
whats activation energy
the minimum amount of energy required for a reaction to take place
whats a reversible reaction
when the products of a reaction can react together to form the origninal reactants
examples of reevrsible reactions
- changing of litmus
-heating anomium chlordide - salts and water of crystalisation
if the first reaction in a reversible reactio is exothermic..
the reverse of it will always be endothermic
what is equlibrium
when the rate of forwards reaction equals the reverse rate of reaction
when does equilibrium occur
in a closed system
how to change amounts of reactants and products at equilibrium
by changing the conditions
what was la chateliers findings
- when conditons are changed to a closed system at equilibrium, the position of equilibrium/reation shifts to cancel out the change
- these changes incl changes in conc, pressure or temp
why is the principle important
because chemists should find the point where conditions are right to get as much product as possible
if the forwards reaction (the creation of products) creates more gas
- an increase in pressure will decrease the amount of products
- a decrease in pressure will increase the amount of products
why does pressure change the amount of products
if you increase the pressure of the forwards reaction, the equilibrium will shift to reduce the pressure in favour of the reaction producing less gas
if we increase the concetnration of the reactantat equilibrium
- the concentration of the product will be icreased until equlibrium is reached again
if temparature is decreased at equilibrium..
the exothermic reaction will be increased so to increase the temparature
if the forwards reaction (creation of products) was endothermic..
- if the temp decreased so would the forwards reaction as the exothermic backwards reaction would increase to raise temp
- if the temp increased so would the forwards reaction
what does pressure effect
reactions involving gasses
if we increase the pressure in a reversible reaction at equilibrium
the equilibrium will shift to the side w the smaller number of molecules
if both sides of the reversible reaction have the same number of molecules
changing pressure does ot affect the point of equilibrium
what is dynamic equilibrium
when there is no effect because the forwards and backwards rate of reactions are happening at the same rate
benefits of le chandeliers principle
we can predict the effect of changes to a system
