Reaction rates and equilibrium
Reaction rates and equilibrium
How fast is a reaction
how fast a reactant is being used up OR how past a product is being formed.
change in concentration/ time
fastest at start because enough reactant. Slows as reactant conc decreases
Surface area of reactants
Larger the surface area for reactions means more successful reactions can take place at one. This leads to a increase in the rate of reaction.
speeds up the rate of reaction by providing a alternative reaction pathway of lower activation energy. Is not used up in the reaction.
same physical state as reactants.
Reacts with reactant and forms intermediate. which then breaks down to from products.
E.g: Making esters with a sulphuric acid catalyst and Ozone depletion (Cl radicals as a catalyst)
Different physical state from the reactants
molecules are weakly bonded to surface of catalyst. After reaction product molecules leave by desorption
E.G Haber process (Fe catalyst), Hydrogenation (Ni catalyst)
increases the number of particles in a volume. They get closer and collide more frequently. Therefore more successful collisions leading to an increase in the rate of reaction
The higher temperature means that particles or molecules have more kinetic energy which means they can more around faster, therefore colliding more often and more successfully. Leading to an increase in the rate of reaction.
Successful collisions are where two molecules collide with the correct orientation and sufficient energy
Monitoring progress of a reaction
decrease in conc of reactions
loss of mass of reactants using a balance
increase in the conc of products
eg volume of gas produced using gas collection
Kc -equilibrium constant
aA+bB :equilibrium cC+dD
Kc =(C)^c (D)^d :heavy_division_sign: (A)^a (B)^b products :heavy_division_sign: reactants
if Kc =1 equilibrium is halfway between reactants and roducts
Kc is greater than 1 equilibrium is more towards products
Kc less than 1 equilibrium is more towards the reactants
Le chateliers principle and dynamic equilibrium
Reactions that take place in the forward and backwards directions
EG Haber process
Rate of forwards reaction=the rate of backwards
as fast as reactants are becoming products, the products are becoming reactants
Concentrations of reactants and products are the same
Le chateliers principle
when a change is subjected to the closed system, the system will readjust to minimise the effect of the change
if increase in the concentration of reactants, there is a decrease in conc of products. The equilibrium shifts left
if increase in the conc of products, the conc of reactants decreases and equilibrium shifts right
dichromate and chromate ions. Yellow and orange
increase in temp shifts system in the endothermic direction (+)
decrease in temp shifts to exothermic position (-)
if the pressure is increased the equilibrium will shift to the side with fewer molecules, therefore reducing the pressure of the system.
does not change the equilibrium
speeds up the reaction (forward and backwards) equally. increases the rate at which equilibrium is reached