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# If a 2nd order reaction has the rate equation $R = k[A][B]$, and the rate constant, $k= 3.67\;M^{-1}s^{-1}$, $[A]$ is $4.5\;M$ and $[B]$ is $99\;M$, what is the rate constant of its pseudo-1st-order reaction?

$\begin{array}{1 1} 363.33\;s^{-1} \\16.515\;s^{-1} \\ 1634.985\;s^{-1} \\ 181.665 \;s^{-1} \end{array}$

Answer: $363.33s^{-1}$
Because $[A]_0 \lt \lt [B]_0$, this is a pseudo first order reaction and we can multiply $k'$ with $[B]_0$ to find $k$.
$\Rightarrow k = 99\;M \times 3.67 M^{-1}s^{-1} = 363.33s^{-1}$
edited Jul 25, 2014