Question

Identify the reaction order from each of the following rate constants.
(i) $k=2.3\times {10}^{-5}Lmo{l}^{-1}{s}^{-1}$
(ii) $k=3\times {10}^{-4}{s}^{-1}$

• A. (i) First order (ii) Second order
  
• B. (i)Second order (ii) First order
  
• C. (i) Zero order (ii) First order
  
• D. None

Answer 1

The correct option is B (i)Second order (ii) First order

(i) Rate of the reaction is given by,

$Rate=k\times [A{]}^x$, where x is the order of reaction

$\left(\frac{mol}{L}\right)=2.3\times {10}^{-5}L\left(mo{l}^{-1}\right)\left(s{)}^{-1}\right[A{]}^x$

$(\frac{mol}{L}{)}^2=constant(s^{-1}\left)\right[\frac{mol}{L}{]}^x$

Therefore, $x=2$ and the reaction is second order

(ii)$Rate=k\times [A{]}^x$, where x is the order of reaction

$\left(\frac{mol}{L}\right)=3\times {10}^{-4}\left(s{)}^{-1}\right[A{]}^x$

$\left(\frac{mol}{L}\right)=constant\left(s^{-1}\right)[\frac{mol}{L}{]}^x$

Therefore, $x=1$ and reaction is first order