Mechanism of a hypothetical reaction\[{{X}_{2}}+{{Y}_{2}}\to 2XY\] is given below: [NEET-2017] |
(i) \[{{X}_{2}}\to X+X(fast)\] |
(ii) \[X+{{Y}_{2}}XY+Y(slow)\] |
(iii)\[X+Y\to XY(fast)\] |
The overall order of the reaction will be |
A) 1.5
B) 1
C) 2
D) 0
Correct Answer: A
Solution :
[a] The solution of this question is given by assuming step (i) to be reversible which is not given in question |
Overall rate = Rate of slowest step (ii) |
\[=k[X][{{Y}_{2}}]\] (1) |
K=rate constant of step (ii) |
Assuming step (i) to be reversible, its equilibrium constant, |
\[{{k}_{eq}}=\frac{{{[X]}^{2}}}{[{{X}_{2}}]}\Rightarrow [X]={{k}_{eq}}^{\frac{1}{2}}{{[{{X}_{2}}]}^{\frac{1}{2}}}\] (2) |
Put (2) in (1) |
\[Rate=k{{k}_{eq}}^{\frac{1}{2}}{{[{{X}_{2}}]}^{\frac{1}{2}}}[{{Y}_{1}}]\] |
Overall order \[=\frac{1}{2}+1=\frac{3}{2}\] |
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