Topic 6- The Rate and extent of Chemical Change Flashcards
what does the rate of a chemical reaction depend on?
The collision frequency of reacting particles (how often they collide). More collisions= faster reaction
the energy transferred during a collision. Particles have to collide with enough energy for it to be successful
what factors affect the rate of reaction?
temperature
the concentration of a solution/pressure of a gas
surface area- changes depending on size of lumps of solid
presence of a catalyst
what does more collision increase
the rate of reaction
how does increasing the temperature increase the rate of reaction
increased temp = particles move faster
therefore they collide more frequently
faster = more energy = more of collisions will have enough energy to make the reaction happen
how does increasing the conc increase the rate of reaction
more concentrated = more particles are moving in the same volume of water
therefore collisions between the reactant particles are more frequent
how does increasing the pressure increase the rate of reaction
more pressure = same number of particles occupy a smaller space
therefore collisions between the reactant particles are more frequent
how does increasing the SA increase the rate of reaction
if one of the reactants is a solid then breaking it up increases its SA to Volume ratio.
this means for the same volume of the solid, the particles around it will have more area to work on
therefore more frequent collisions
how does using a catalyst increase the ROR
catalyst decreases the activation energy by providing an alternative reaction pathway with a lower activation energy
enzymes are biological catalysts
how is equilibrium reached
when the reactants react their concentrations will fall so the forwards reaction will slow down
BUT as more and more products are made and their concs rise, the backward reaction will speed up
after a while the reactions will both be going at he same rate = EQUILIBRIUM
what’s a dynamic equilibrium
when both reactions are still happening but there’s no overall effect.
this means that the concs of reactant and products have reached a balance and won’t change
where does equilibrium take place
in a closed system
what is a closed system
none of the reactants or products can escape and nothing else can enter/get in
if the equilibrium lies to the right, it means that…
the concentration of products is greater than that of the reactants
if the equilibrium lies to the left, it means that…
the conc of reactants is greater than the conc of products
what does the position of equilibrium depend on
temperature
pressure (only gases)
conc of reactants and products
if the reversible reaction is endothermic in one direction, it will be…
exothermic in the other
explain endo and exothermic reactions in reversible reactions
the energy transferred form the surroundings by the endothermic reaction is equal to the energy transferred to the surroundings during the exothermic reaction
what does Anhydrous mean
without water
what does hydrated mean
with water
give an example of endo and exo reaction
thermal decomposition of hydrated copper sulfate
if you heat blue hydrated copper (2) sulfate crystals, it drives the water off and leaves anhydrous copper (2) sulfate powder. this is endothermic
if you then add water to the powder, you get blue crystals back again. this is exothermic
what is Le Chatelier’s Principle
the idea that if you change the conditions of a reversible reaction at equilibrium the system will try to counteract that change
what happens to the reaction if you decrease/ the temperature
the equilibrium will move in the exothermic direction to produce more heat, therefore you will get more products in the exothermic direction and fewer in the endothermic direction
increase = opposite idea
what happens if you increase/decrease the pressure
the equilibrium tries to reduce it so moves in the direction where there are fewer molecules of gas
decrease = opposite idea
what happens if you decrease/increase the concentration
if you increase the conc of the REACTANTS the system tries to decrease it by making more products
if you decrease the conc of PRODUCTS the system tries to increase it again by reducing the amount of reactants
