Consider the two hypothetical reactions given below: |
I. \[aA\to products,k=xmo{{l}^{-1}}L{{\min }^{-1}}\] |
II. \[bB\to products,k=y{{\min }^{-1}}\] |
The half-lives of both the reactions are the same, equal to 1 hr when molar concentration of the reactant is 1.0 M in each case. If these reactions are started at the same time taking 1 M of the reactant in each case, the ratio \[\left[ A \right]/\left[ B \right]\] after 3hr will be: |
A) \[0.5\]
B) \[4\]
C) \[1\]
D) \[~2~\]
Correct Answer: D
Solution :
[d]Units of k indicate that reaction I is of second order and reaction II is of first order. For I reaction, \[{{t}_{1/2}}\alpha 1/a,\] first\[{{t}_{1/2}}=1hr\], second \[{{t}_{1/2}}=2hr\] |
\[\left[ A \right]=1M\xrightarrow{1hr}0.5M\xrightarrow{2hr}0.25M\] |
\[\left[ B \right]=1M\xrightarrow{1hr}0.5M\xrightarrow{1hr}0.25M\] |
\[\xrightarrow{1hr}0.125M\frac{\left[ A \right]}{\left[ B \right]}=\frac{0.25M}{0.125M}=2\] |
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