PAGES 47-50 COLLISION THEORY i. Reactant particles States thhtinorderforachemichlreactiontoocwrbetwee.nu : - must collide with correct orientation particles . . 8- 88×-8 the " 8 8 products formed particles mustoollide with sufficient energy to overcome the @hergybarrurcactivationenergyItorthlrehction.oif donothaveenergyegualtoorgrehlerthhnea 2. Reactant colliding particles d H → yENERGY Bss BE unsuccessful bounce apart , . bounce off ④ # , → TO a successful ④ - Oyo " Cl Cl ACTIVATION ENERGY Defined as minimum amount of kinetic energy that barrier colliding particles musthavetoraohemichlreactiontooavr Energy . . transition state ^ - highest energy state of hewbondsblingformldwhil.ie/rea an.-?aIuondsare a f. exothermic reaction Ease between reactants and transition stale energy arehction , indication of level profile - . . Ea Products Reaction progress kinsmen . reaaigeroensteqwmi.qarqyiowonsnggganige.ie;Ef'either ↳ doesn't change with temperature . MAXWELL BOLTZMANN DISTRIBUTION - 100k - E€# 300k § 600k it Indicates the number -0 particles with enough activation energy with relation to temperature 1000k E s 1000 O ' RATE OF REACTION rate - - 2000 mollwlhrsplldlms ) : ' change inancehtrationofareauhhtorproductperunith.me . deorehseincrehdaht3-or-screaaantchangeinti.me St Factors • affecting rate temperature - when : particles are heated , theygainkineticehergyandmovesesler . higher probability of successful collisions b. greater proportion of reactant particles collide withenergyeguhltoorgrehlerthantheea a. frequency otaxlisions For most reactions +10°C . - - increases , 2x rate . . 300k Eh Eh ¥t↳¥tA÷h E E D D I I Ea - S kinetic energy kinetic energy - - • 400k f f - peakshiftstotherightiinureaseinthemosttikdyvalueofkeot particles .tt -9 average ke wrvefhaltensibewmesbroader.to/a1areaanstant increase . . inareaundertothehghtofta greater fraction of particles will have enough Ea . . concentration increase inwnantration increases rate increased # of particles means an increased frequency - , . collisions more likelihood of successful collisions between reactant particles - - • . pressure - increase in pressure means . moregaspartiaesinagivenvolume , more collisions . of • surface area breaking up into smaller pieces increase in surface area per unit volume increase in - , , rate of reaction . ROLE OF CATALYSTS what are catalysts ? substances which increase the rate of a reaction energy . It remains chemically unchanged so it by providing an alternate reaction pathway which has a lower activation may be reused . ^ ¥fy iiiineieaniiinoiiiaainsist . , # -9 Maxwell Boltzmann distribution curve - - lower Ea ( Ea eats) , greater proportion of reactant particles have enough Ea . ^ it.ie#.A. Not enough kinetic energy RATE EXPRESSION Gives the relationship between reactant concentrations and the rate of reaction can be used to predict the rate of a reaction ( with known concentrations) and establish mechanisms : . . W k - X t → Y t 2 rate constant for arxn at a temp - dependent CWVCXI , rate - - K ( WITH b specific temperature . . concentrations of reactants a/b order of rxn with respect to reactants factor by which the concentration of a reactant affects the rate at rxn Oil or 2 Overall rxn order atb - - . . - - EFFECT ON RATE EXAMPLE ORDER rate zero - - ( moldm-35 ) KCMO ' , Scone doesn't affect rate rate first - - RCN rate x2 rate -_ RCW ) . , i Second . Directly proportional banc .x2 ' (s ) - Independent ' , . Square Ofw , sconce .Wx3, (mot 'dm35 ) ' increases rate 32 by . Third ' (mot 2dm65 ) - DETERMINING OVERALL ORDER FROM GRAPHS concentration time - A : A straight A EM .¥L.¥L zero order - First-order exponential - O O O e e e t t t u v u TIME Rate concentration - Mero order - avadratic Z Z Z second order → TIME TIME : rate independent Afirstorder directly Asewndorder parabolic ¥t¥h¥w - toanantratien . - CONCENTRATION - proportional - CONCENTRATION - curve - CONCENTRATION HALF LIFE - FIRST ORDER KINETICS t :(th) time ittakes for the concentration of a reactant to decrease by half half life is constant and independent of the initial concentration of reactants HAH LIFE For first order reactions, the - - . . - . ¥÷¥i Z 8 2nd half - life 3rd - half life REACTION MECHANISMS many reactions happen as a sequence of elementary steps RATE DETERMINING STEP (RDA determines the rate at which the reaction can proceed step with the energy rate expression determined by compounds before the slow step : . - - . . highest activation . Eg NO 215) . NO 3G) ( Ocs) t rate lb NOW . NO cost t t - → → NO 3G) NOUS) t t NO Csl SLOW ( 0215) FAST RCN 0232 NOCs ) F #s) FAST NHS) t this, →NICS) t th Ocs, SLOW s ) t Hug , → Nz CS ) t Hz OCS) FAST rate RCN 072 CHA - - overall equation - - 2 NO est 2 Hug , t → Nus) t 2h20 CS) MOLECULARITY determines number of reactant particles in an elementary step vnimollwlhr A → products rate KCA] decompositiondissociation bimolewlhr At A → Products rate NAY collision t reaction - . - - - , , - - - , At B turmoilWthr - → products , rate At ATA → At At B At Btc = RCA] CBI NAP rate KCATZCB) products , rate → → products , products . , - - - - rate - - i collision + reaction KIAT CB) IC) Requirementfor simultaneous collision of 3 reactant particles with correct orientation alermohewlhr elementary step occurring is low . means the probability of REACTION INTERMEDIATES t TRANSITION STATES REACTION INTERMEDIATE a species that is formed from the reactants in a vessel which then the products do not appear in overat leg common feature of multi step reactions : goes on to further form - . . . TRANSITION STATE IACTIVATED COMPLEX : highest energy slate on a reaction coordinate indicates . bonds are being formed and old bonds are being broken simultaneously point at which new . TS I ¥ftAE ^ TS 2 P E intermediate £ ¥ A # # REACTION PROGRESS ARRHENIUS EQUATION t ACTIVATION ENERGY ACTIVATION ENERGY rate constant R is temperature : described . . by the Arrhenius eh nation - K Ew - dependent Relationship between temperature and . - is . ④④⑤ Arrhenius constant , pre exponential / frequency factor l Euler 's number in Tmo t Ea activation A k - . - . - R T - - energy universal gas onstunt ' - 8.3IT R , Absolute temperature in k ' ' m ol ' . ARRHENIUS CONSTANT A accounts for frequency of collisions and : . EXPONENTIAL FACTOR certain temperature - . probability of correct orientation !geometry EalRT traction of molecules which have sufficient kinetic energy to overcome the : . =D increase in temperature increase in = k and rate . . Ea at a GRAPHICAL DETERMINATION OF Ea Infra - 1nA : , natural rewritten toformlineht equation that - to determine Ea Ay intercept tht ) )\ - S E - 1nA fief)¥ - - - - R ¥2 - - " Ea - gradient 't ¥ ^ Higher Ea Eun were , - R Fei # It H - . - ¥ - - - n Ink . Eacalwbrtions gradient EI - "adieu hog the equation
