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Solved Examples-Part1
Solved Examples for Molecularity and Order of Reaction
Example : The experimental data for the reaction
2A + B2 → 2AB
is as follows:
|
Expt. No.
|
[A]
(mol L-1)
|
[B2]
(mol L-1)
|
Rate
(mol L-1 s-1)
|
|
1.
2.
3.
|
0.50
0.50
1.00
|
0.50
1.00
1.00
|
1.6×10-4
3.2×10-4
3.2×10-4
|
Write the most probable equation for the rate of reaction giving reason for your answer.
Solution : From an examination of above data, it is clear that when the concentration of B2 is doubled, the rate is doubled. Hence the order of reaction with respect to B2 is one.
Further when concentration of A is doubled, the rate remain unaltered. So, order of reaction with respect to A is zero.
The probable rate law for the reaction will be -dx/dt = k[B2][A]0 = k[B2]
Alternatively Rate = k[B2]α
1.6 × 10-4 = k[0.5]α
3.2 × 10-4 = k[1]α
On dividing we get α = 1
.·. Rate = k[A]0[B2]1 = k[B2]
Example : For the reaction
A + 2B → 2C
the following data were obtained.
|
Expt. No.
|
Initial concentration (mol L-1)
[A] [B]
|
Initial reaction rates (mol L-1min-1)
|
|
1.
2.
3.
4.
5.
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1.0
2.0
3.0
1.0
1.0
|
1.0
1.0
1.0
2.0
3.0
|
0.15
0.30
0.45
0.15
0.15
|
| |
|
|
|
Write down the rate law for the reaction.