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  •  What will be the unit of rate constant (k) for a third order reaction?  Option: 1 <img alt="\mathrm{s}^{-1} \\" src="h

 What will be the unit of rate constant (k) for a third order reaction?

 

Option: 1

\mathrm{s}^{-1} \\


Option: 2

\mathrm{~mol}^2 \mathrm{~L}^{-2} \mathrm{~s} \\


Option: 3

\mathrm{~mol}^{-2} \mathrm{~L}^2 \mathrm{~s}^{-1} \\


Option: 4

\mathrm{~mol}^{-1} \mathrm{~L}^{-2} \mathrm{~s}


Answers (1)

best_answer

Generalized formula for the unit of rate constant (k) for a \mathrm{n^{\text {th }}}  order reaction. Let,
\mathrm{A \rightarrow} Products
is a \mathrm{n^{\text {th }}}  order reaction.
Rate \mathrm{(R)=k[A]^n}
Units of        \mathrm{k=\frac{\text { Units of rate }}{\text { Units of }[A]^n}}
Since, rate is change of concentration w.r.t time
So, units of rate are   \mathrm{\frac{\mathrm{mol}}{\mathrm{L} \cdot \mathrm{s}}}
Units of      \mathrm{k=\frac{\frac{m o l}{L \cdot s}}{\left(\frac{m o l}{L}\right)^n}}

Units of    \mathrm{ k=\left(\frac{m o l}{L}\right)^{(1-n)} \times s^{-1}}
For a third order reaction, n=3 :
Units of     \mathrm{ k=\left(\frac{m o l}{L}\right)^{-2} \times s^{-1}=m o l^{-2} L^2 s^{-1}}.

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avinash.dongre

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