Question

The pre-expontial factor in the Arrhenius equation of a first order reaction has the units -

• A. $\text{mol}{L}^{-1}{a}^{-1}$
• B. $L{\text{mol}}^{-1}{s}^{-1}$
• C. $s^{-1}$
• D. $\text{None of these}$

Answer 1

The correct option is C $s^{-1}$

$k=A{e}^{-Ea/RT}$
$\text{Unit of k = unit of A}$
$(As{e}^{-Ea/RT}\to \text{unitless})$
For first order reaction,
$\text{Unit of}k=s^{-1}$ or $mi{n}^{-1}$ or $h^{-1}$
$\therefore$
$\text{Unit of A will be}=s^{-1}$