For the following rate law determine the unit of rate constant. Rate $=-\frac{d[ R ]}{d t}=k[ A ]^{\frac{1}{2}}[ B ]^{2}$

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The total order of reaction $n=\frac{1}{2}+2=\frac{5}{2}=2.5$ Rate $k[\mathrm{~A}]^{\frac{1}{2}}[\mathrm{~B}]^{2}=[\mathrm{R}]^{\frac{5}{2}}$

$\therefore k=\frac{\text { Rate }}{[\mathrm{R}]^{5 / 2}}$

$\therefore$ unit of $k=\frac{\text { unit of rate }}{\text { (unit of concentration) }^{5 / 2}}$

$=\frac{\left(\mathrm{mol} \mathrm{L}^{-1}\right)^{1} \mathrm{~s}^{-1}}{\left(\mathrm{~mol} \mathrm{~L}^{-1}\right)^{\frac{5}{2}}}$

$=\left(\mathrm{mol} \mathrm{L}^{-1}\right)^{1-\frac{5}{2}} \mathrm{~s}^{-1}$

$=\left(\mathrm{mol} \mathrm{L}^{-1}\right)^{-\frac{3}{2}} \mathrm{~s}^{-1}$

$=(\mathrm{mol})^{\frac{-3}{2}}\left(\mathrm{~L}^{-1}\right)^{\frac{-3}{2}} \mathrm{~s}^{-1}$

$=\mathrm{mol}^{\frac{-3}{2}} \mathrm{~L}^{\frac{+3}{2}} \mathrm{~s}^{-1}$

If the order of reaction $=\frac{5}{2}$ then unit of rate constant $k$ is $\mathrm{L}^{\frac{+3}{2}} \mathrm{~mol}^{\frac{-3}{2}} \mathrm{~s}^{-1}$.

Similar Questions

For the first order decompsition reaction of $N_2O_5$, it is found that - 

$(a)$   $2N_2O_5\rightarrow\,\,4NO_2(g)+O_2(g)-\frac{d[N_2O_5]}{dt}=k[N_2O_5]$

$(a)$   $N_2O_5\rightarrow\,\,2NO_2(g)+1/2\,\,O_2(g)-\frac{d[N_2O_5]}{dt}=k'[N_2O_5]$

which of the following is true ?

The rates of a certain reaction $(dc/dt)$ at different times are as follows

Time                                 Rate (mole $litre^{-1}\,sec^{ -1}$ )

$0$                                        $2.8 \times {10^{ - 2}}$

$10$                                      $2.78 \times {10^{ - 2}}$

$20 $                                     $2.81 \times {10^{ - 2}}$

$30$                                       $2.79 \times {10^{ - 2}}$

The reaction is

For the reaction $A + B \to $ products, what will be the order of reaction with respect to $A$ and $B$ ?

   Exp.    $[A]\,(mol\,L^{-1})$   $[B]\,(mol\,L^{-1})$   Initial rate    $(mol\,L^{-1}\,s^{-1})$ 
   $1.$  $2.5\times 10^{-4}$  $3\times 10^{-5}$  $5\times 10^{-4}$
   $2.$   $5\times 10^{-4}$  $6\times 10^{-5}$  $4\times 10^{-3}$
   $3.$   $1\times 10^{-3}$  $6\times 10^{-5}$  $1.6\times 10^{-2}$

Define following term / Give definition :

$(1)$ Elementary reaction

$(2)$ Complex reaction

For a reaction $\mathrm{A} \xrightarrow{\mathrm{K}_4} \mathrm{~B} \xrightarrow{\mathrm{K}_2} \mathrm{C}$

If the rate of formation of $B$ is set to be zero then the concentration of $B$ is given by :

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