NEET Solved Paper 2017 Question 26
Question: Mechanism of a hypothetical reaction $ X _2+Y _2\to 2XY $ is given below:
(i) $ X _2\to X+X(fast) $ (ii) $ X+Y _2XY+Y(slow) $ (iii) $ X+Y\to XY(fast) $ The overall order of the reaction will be
Options:
A) 1.5
B) 1
C) 2
D) 0
Show Answer
Answer:
Correct Answer: A
Solution:
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=kk _eq^{\frac{1}{2}}{{[X _2]}^{\frac{1}{2}}}[Y _1] $ Overall order $ =\frac{1}{2}+1=\frac{3}{2} $
