Time (min) | |
0.400 0.289 0.209 0.151 0.109 | 0.00 20.00 40.00 60.00 80.00 |
Answer:
Rate expression is the rate law giving rate in terms of molar
concentration of the reactants.
Rate of disappearance of
Rate of disappearance of
Complete rate is given by rate law
?(i)
[1]
where [A] and [B] are the molar concentration of the reactants
A and B respectively.
a: order wrt A
b : order wrt B
k : is called rate constant
If [A] = [B] =1 at a
given time then by
Eq. (i) Thus, rate constant is equal to the rate expression when molar
concentration of each reactant is.
(b) (i) For first-order reaction
Average value of
(ii)Initial rate
[1]
(iii) Let time (concentration of be 0.350
[1]
Or
(a) (i) Order of reaction
The number of reactants whose concentration
change and which are involved in rate-determining step
(slow step) is called order of reaction.
product
a = order wrt A
b = order wrt B
We assume that concentration of A and B changes and
both the reactants are involved in rate-determining step.
Case I Concentration of A does not change and slow step
product
thenorder = 2
wrt B
Case II Cone of B does not change and slow step product such
that
Then order = 1 wrt A
[1]
Order can be whole number fractional and even negative.
(ii) Elementary step in a reaction
An elementary reaction is a reaction that occurs in a single
step, with no experimentally detectable reaction intermediates. If no such
intermediate can be detected or need to be postulated to interpret the behaviour,
a reaction is assumed tentatively to be elementary.
Initially it was assumed to be elementary. But this takes
place in part by a mechanism involving following elementary steps.
[1]
(b) For first order reaction
Initial concentration =0.10 M time =3.0 h =180 min
Concentration after 180 min =(a-x)
Antilog
of 0.3908
[1]
Set
(a)
(a-x)
Time
K
(i)
0.400 M
0.289
20 min
0.01625
(ii)
0.400 M
0.209
40 min
0.01623
(iii)
0.400 M
0.151
60 min
0.01624
(iv)
0.400
0.109
80 min
0.01625
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