Rates of Reactions - Term 4 Flashcards
2 general ways to measure the rate of a reaction
measure how quickly the product is made
measure the rate the reactants disapear
4 main factors considered when studying rates of reaction
conc gradient (of solutions)
temperature
surface area (solids)
pressure (gas)
what is collision theory
for a reaction to occur, particles must collide with each other. these collisions must be equal to or greater than the activation energy . energetic collisions allow bonds to be broken
whats activation energy
the minimum amount of energy needed for a reaction to occur
what happens if particles dont reach activation energy
they bounce off each other, not collide
how to work out rate of reaction (graph)
draw a tangent and find its gradient
how to find average reaction time (graph)
draw triangle from point given and find gradient
why might a reaction begin producing the reactant rapidly and slow down (in collision theory)
frequent successful collisions needed for reaction to occur. as the concentration of the reactant decreases, collisions become less successful
explain the relationship between concentration (of solutions) and rate of reaction (in collision theory)
increasing the concentration of reactants means there are more particles to react in the same volume, leading to more frequent collisions and a faster rate of reaction
Calcium carbonate (marble chips) and hydrochloric acid RQP practical is taking place. what are the two methods for measuring rate of reaction
gas collection (with a syringe)
mass loss (using a mass balance)
disadvantage of gas collection
gas is in air / increments too small
advantage of mass collection
accurate
how does concentration affect rate of reaction
higher conc = faster rate of reaction
how does surface area affect rate of reaction
larger surface area = faster rate of reaction
explain the relationship between surface area and rate of reaction affect the rate of reaction
as surface area per volume increases , there is a greater area of contact between the solid and other reactant over which collisions can occur. therefore, there are more frequent collisions and a faster rate of reaction
what RQP is used for investigating temperature and rate of reaction
how temperature affects the rate of reaction between hydrochloric acid and sodium thiosulphate
what RQP is used to investigate the relationship between surface area and rate of reaction
the reaction between calcium carbonate (marble chips) and hydrochloric acid
what is the product of the temperature RQP between hydrochloric acid and sodium thiosulphate ( and how is the rate of reaction measured)
sulphur (how long it takes the yellow solid to block our view of the cross under the flask)
affect of temperature on rate of reaction
higher temperature = faster rate of reaction
explain the relationship between temperature and the rate of reaction (in collision theory)
the particles gain kinetic energy . the particles move faster collide more energetically more frequent collisions can occur that will exceed activation energy. therefore, the rate of reaction is faster
what is a catalyst
a catalyst speeds up the rate of a reaction without being used in the reaction
how does a catalyst work
a catalyst works by providing an alternative path for the reactant that has a lower activation energy than the uncatalysed reaction
why are catalysts important to the energy
they lower energy needed for a reaction, (saving money) and make reaction faster (more product produced faster)
how can a catalyst be poisoned
if surface is coated with another chemical
