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.
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.
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
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
rate equation continued
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