JIPMER Jipmer Medical Solved Paper-1997

  • question_answer
    At \[250{}^\circ C,\] the time for half-change for the thermal dissociation of \[{{N}_{2}}{{O}_{5}}\] is 5.7 hours. The specific rate constant is given by:

    A)  \[\frac{1}{5.7}\text{hou}{{\text{r}}^{-1}}\]                        

    B)  \[\frac{\ln \,2}{5.7}\text{hou}{{\text{r}}^{-1}}\]              

    C)  \[\ln \frac{2}{5.7}\text{hou}{{\text{r}}^{-1}}\]

    D)         \[0.5\,\,\text{hou}{{\text{r}}^{-1}}\]

    Correct Answer: B

    Solution :

    The thermal dissociation of \[{{N}_{2}}{{O}_{5}}\] is a first order reaction. Hence, for it \[k=\frac{1}{t}\ln \,\frac{a}{(a-x)}\] For half-change,                 \[k=\frac{1}{{{t}_{1/2}}}\ln \,\frac{a}{\left( a-\frac{a}{2} \right)}\] \[=\frac{1}{{{t}_{1/2}}}\cdot \ln 2\] \[\therefore \]  \[k=\frac{\ln \,2}{5.7}\text{hou}{{\text{r}}^{-1}}\]


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