Question

If the first order reaction involves gaseous reactant and gaseous products the units of its rate are:

• A. $atm$
  
• B. $atm-sec$
• C. $atm-{sec}^{-1}$
• D. ${atm}^2-{sec}^2$

Answer 1

Answer: (C)

$atm-{sec}^{-1}$

The correct answer is C

The rate of the first-order reaction can be written as:

where $k$ is the first-order rate constant. The units of k are $s^{-}1$. Since only time factor appears in representing the unit it does not matter we are talking about the Concentration or partial pressure of reactant.

So the unit will be the same that is $s^{-}1$ (per second). This is by the following equation if the concentration is replaced by partial pressure in first order reaction.