For a first order chemical reaction,

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(C) . The Arrhenius equation for the rate constant $k$ is $k = A e^{-E_a / RT}$,where $A$ is the pre-exponential factor.Since the term $e^{-E_a / RT}$

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the dimension of Arrhenius pre-exponential factor is reciprocal of time.

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(C) . The Arrhenius equation for the rate constant $k$ is $k = A e^{-E_a / RT}$,where $A$ is the pre-exponential factor.Since the term $e^{-E_a / RT}$ is dimensionless,the dimension of $A$ is equal to the dimension of $k$.For a first-order reaction,the dimension of $k$ is $	ext{time}^{-1}$.Therefore,the dimension of $A$ is also $	ext{time}^{-1}$,which is the reciprocal of time.Regarding other options:For a first-order reaction,the rate of reaction is directly proportional to the reactant concentration.The half-life $t_{1/2} = \frac{0.693}{k}$,which is $69.3 \%$ of $\frac{1}{k}$.The concentration of the reactant changes with time according to the equation $[A]_t = [A]_0 e^{-kt}$,which represents an exponential decay,not a linear one.

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