Question

The rate constant of third order reaction is:

• A. $ \text{mol}\,{{\text{L}}^{-1}}{{\text{S}}^{-1}} $
• B. $ \text{mo}{{\text{l}}^{-2}}\,{{\text{L}}^{2}}{{T}^{-1}} $
• C. $ \text{mo}{{\text{l}}^{-1}}\,\text{L}{{\text{s}}^{-1}} $
• D. $ mo{{l}^{-2}}{{L}^{-1}}{{S}^{-1}} $

Answer 1

Answer: (B)

For the reaction of nth order
$k=\frac{1}{\text { time }} \frac{1}{[\text { conc. }]^{(n-1)}}$
For 3rd order reaction $n=3$
$\therefore $ units of $k=\frac{1}{\text { time }} \times \frac{1}{(\text { conc. })^{3-1}}$
$=\frac{1}{\text { time }} \times \frac{1}{\left(m o l^{-1}\right)^{2}}$
$=m o l^{-2} L^{2} T^{-1}$