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How does nature of reactants increase reaction rate
if Rapid Rate, it does not involve rearrangement
simple collision of two ions, no complex bond breaking or forming involved
if slow rate, it involves complex bond rearrangement
complex bond breaking and bond forming involved
complex molecular collisions of sufficient energy and orientation
Surface Area (state of subdivision)
to react, substances must be in contact
the larger the total surface area of the solid, the more of it will be in contact with other reactants and faster reaction rate
Concentration of gases
concentration of gases can increase when pressure is increased
Temperature
generally, raising temp increases rate of chemical reaction
as temp rises, so too does velocity of reacting particles
this increases frequency of collisions (increases number of successful collisions)
force/energy of collisions increases (increases number of particles with sufficient energy to overcome activation energy, increasing RoR)
Catalyst
speeds up the rate of a reaction without itself being permanently consumed in the reaction
catalysts provide reactants with an alternate reaction path of lower activation energy
Chemical Equillibrium
when the rate of forward and reverse reactions are equal
when the concentration of all species in the system are constant
closed system (constant temp)
constancy of macroscopic properties (observable properties)
equal but opposing rates of reaction
reactions continue at molecular level even after equillibrium established (dynamic)
Physical Equillibrium
3 physical systems where dynamic equillbrium can occur: phase equillbrium, solubility equillibrium
Vapour/Liquid Equillibrium
when equillibrium is established between a liquid and its vapour, the rates of condensation and evaporation will be equal
Solution Equillibrium
when equillibrium is established between undissolved solute and solute in solution, rates of dissociation and of crystallisation will be equal
Equillibrium Constant
mathematical relationship between concentrations of reactants and products of reaction at equilibrium for all concentrations and pressure at a particular temperature
if K < 1, reaction favours reactants (conc of reactants is higher)
if K > 1, reaction favours products (conc of products is higher)
if K = 1, significant conc of both products/reactants at equilibrium
provides no indication of rate of reaction
Changes to Equillibrium
if system is disturbed by change in temp of system, conc of component species or volume of component gas, system will tend to re-establish equilibrium by forming more reactants or products
Effect of Catalysts on Equillibrium
have no effect on position of equilibrium
have no effect on equilibrium constant
equally affects forward and reverse rates
no equilibrium shift
Le Chatelier's Principle
if a chemical system at equillibrium is subjected to a change in conditions, the system will re-establish equillibrium in such a way as to partially counteract the imposed change
Effect of Temperature on Equillibrium
if temp of system is increased, system re-establishes equilibrium in such a way to partially decrease temp
endothermic reaction is favoured to absorb heat
when temp changes, equilibrium constant (K) changes
when temp changes, rate of both forward and reverse reaction changes, e.g when temp increase both forward and reverse increase, but one is favoured (at a greater rate)
endothermic reaction is always affected more (on reaction rate graph)
Effect of Change in Pressure/Volume on Equilibrium
if volume of gaseous equillibrium system is changed, then conc. of substances making up the system is changed
if volume is decreased, pressure increases
system will partially counteract to decrease pressure
to decrease pressure, no. of total molecules should decrease
this means side with less particles is favoured
Open System
allow matter and energy exchange with the surroundings
Closed System
only allow energy exchange, not matter
Heterogeneous System
system that involve reactants and products in different phases
Homogeneous System
involve all reactants and products in the same phase
Reaction between CaCO3 and H+
CaCO3 + H+ ←—> Ca2+ + HCO3-
Kyoto Protocol
aims to reduce greenhouse gas emissions globally
Adding Inert Gas
increases total pressure
no effect on partial pressure of reactants
no effect on collisions between reactants
no change in reaction rate
