3.10 Reaction Rates and Equilibrium

change in concentration of a reactant or product in given time

change in conc/time

-fastest at start as reactant highest conc
-slows as reaction proceeds ad reactant used up
-stops when reactants fully used

-concentration
-pressure
-temp
-catalyst
-sa of solid reactant

2 reacting particles must collide for reaction to occur

molecules collide then bounce off eachother and remain chemically unchanged

-particles collide with correct orientation
-particles have sufficient energy to overcome activation energy

increases bcos number of particles increase in same volume so closer together so collide more frequently so more effective collisions

increases bcos gas molecules closer together so collide more so more frequent effective collisions

-monitoring removal of reactant (decrease concentration)
-following formation of product (increase concentration)

-monitor volume of gas produced at regular intervals
-monitor loss of reactants using balance

substance that changes rate of chemical reaction without undergoing permanent change itself

provides alternate reaction pathway of lower activation energy

catalyst with same physical state as reactants

-catalyst reacts with reactant to form intermediate
-intermediate breaks down to give product
-catalyst regenerates

making esters with sulfuric acid as catalyst

ozone depletion with Cl radicals as catalyst

catalyst with different physical state from reactants

-reactant molecules absorbed (weakly bonded) onto surface of catalyst where reaction takes place
-after, product molecules leave surface by desorption

-reduce temp and energy needs
-less electricity and fossil fuels used
-which cuts cost increasing profit and is more sustainable

the spread of molecular energies in gases

total number of molecules

no molecules have 0 energy

no max energy so line never meets x axis (unless curve reached infinity)

-average energy increases
-more molecules have higher energy
-graph stretched over greater range of energy values
-peak is lower and further along (at higher energy)
-number of molecules same so area beneath curve stays same

-more molecules reach activation energy
-so greater proportion of successful collisions so greater rate of reaction
-collisions are also more frequent due to greater speed of molecules (not as important)

due to lower activation energy greater proportion of molecules have energy that reaches activation energy