| I \[a\text{ }A\to \]Products, \[k=x\,mo{{l}^{-1}}\text{ }L\text{ }mi{{n}^{-1}}\] |
| II \[bB\to \]Products, \[k=y\,mi{{n}^{-1}}\] |
| 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 1M of the reactant in each case, the ratio [A]/[B] after 3 hr 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 first order. For I reaction, \[{{t}_{1/2}}\propto 1/a\] first \[{{t}_{1/2}}=1\,hr,\] second \[{{t}_{1/2}}=2hr\] \[[A]=1M\xrightarrow{1\,hr}0.5M\xrightarrow{2\,hr}0.25M\] \[[B]=1M\xrightarrow{1\,hr}0.5M\xrightarrow{1\,hr}0.25M\xrightarrow{1hr}0.125M\]\[\frac{\left[ A \right]}{\left[ B \right]}=\frac{0.25\text{ }M}{0.125\text{ }M}=2\]
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