kinetics/ rate of reaction simple rate equations determination of rate equation 3.0 / 5 ChemistryRatesA2/A-levelAll boards Created by: DamianCreated on: 12-09-09 13:53 kinetics RECAP Rate= change in concentration / time for change to occour collision theory A reactions will only happen if the reacting particles: 1, Collide in correct orientation and 2, have collision energy EQUAL TO or GREATER THAN the ACTIVATION ENERGY Ea=minimum collision energy needed for the reaction to occur. 1 of 5 RATES OF REACTION RATE OF REACTION = rate of change of concentration of a named reactant or prouduct with respect to time. rate is measured in mol dm-3 s-1 ( could be minutes or hours depending on the speed of reaction). RATE DECREASES AS TIME PROCEEDS reactants get used up, fewer collisions, lower reactin rate. 2 of 5 rate equations RATE EQUATIONS = matematical equations showing How rate of REACTION varies with the Concentration of ANY Particular Reactant. IN GENERAL , the rate eqaution for reactant "A" is in the form: RATE = K[A]p p= order of reaction 0,1 or 2 where A = the molar concentration ofreactant "A" K= the Rate Constant for the reaction power P= the Order reaction for A 3 of 5 working out the RATE EQUATIONS RATE =K [H2]a [NO]b table 1 initial conc (mol dm-3) initial rate (mol dm-3 s-1) ept H2 NO 1 0.01 0.025 2.4x10(-6) 2 0.005 0.0025 1.2x10(-6) 3 0.01 0.0125 0.6x10(-6) ept 1 and 2 [NO] constant [H2] x2 ratex 2 so its first (1) order w.r.t [H2] a=1 ept 1+3 [H2] constant [NO]x2 rate x4 (22) second order w.r.t [NO] b=2 overall order=3 (just add both together) RATE= k [H2] [NO]2 4 of 5 rate equation continued experiment 1 K= RATE = 2.4x10(-6) = 0.384 mol-2 dm6 s-1 [H2] [NO]2 (0.01) (0.025)2 k= mol dm-3 s-1 (mol dm-3) (mol dm-3)2 or mol2 dm-6 those the same on top as buttom cancel each other out leaving s-1 mol-2 dm6 s-1 mol2 dm-6 5 of 5

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