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The reaction between \mathrm{A\: and\: B} is carried out for different initial concentrations and the corresponding half life times are measured

\mathrm{\left [ A \right ]_0} \mathrm{\left [ B \right ]_0} \mathrm{1y_2}
500 10 60
500 20 60
10 500 60
20 500 30

the rate law of reaction will be:-

Option: 1

\mathrm{rate\Rightarrow K \left [ A \right ]\left [ B \right ]}


Option: 2

\mathrm{rate\Rightarrow K \left [ A \right ]^{1}\left [ B \right ]}


Option: 3

\mathrm{rate\Rightarrow K \left [ A \right ]\left [ B \right ]^{3}}


Option: 4

\mathrm{rate\Rightarrow K \left [ A \right ]^{2}\left [ B \right ]^{2}}


Answers (1)

best_answer

Experiment -1

\mathrm{\left([A]_0\right)_2=500 }      \mathrm{(t1 / 2)_2=60}

\mathrm{\left.[ B]_0\right)_2=10}

\mathrm{ t_1/2 \propto \frac{1}{[A]_0^{n-1}} }

Experiment -2

\mathrm{ \left([A]_0\right)_2=500 }                 \mathrm{ \quad\left(t \frac{1}{2}\right)_2=60 }

\mathrm{ \left([B)_0\right)_2=20 }                             

\mathrm{{\left[\frac{[B_0]_2}{\left[B_0\right]_1}\right]^{n-1}=\left(\frac{\left[t_ 1/2\right]_1}{\left[t_ 1/2\right]_2}\right)} }        

\mathrm{{\left[\frac{20}{10}\right]^{n-1}=\left(\frac{60}{60}\right)} }

\mathrm{\left ( 2 \right )^{n-1}\Rightarrow 1 }

\mathrm{\left ( 2 \right )^{n-1}\Rightarrow 2^{0} }

\mathrm{n-1 =0 }

\mathrm{n=1}       [First order w.r.t.[B] ]

Here \mathrm{[A]_0} concentration doesn't change so half life depends on \mathrm{[B]_0} only.

Experiment-3                              Experiment-4

\mathrm{{\text { }}{\left\{[A]_0\right\}_3= 10}}                         \mathrm{\left ( \left [ A \right ]_0 \right )_4=20}

\mathrm{{\{[B_0]\}_3=500}}                      \mathrm{\left ( \left [ B \right ]_0 \right )_4=500}

\mathrm{{\left(t _1/2\right)_3=60}}                         \mathrm{\left ( t_1/2 \right )_4=30}

\mathrm{\frac{\left([A]_0\right)_4}{\left((A]_0\right)_3}=\left(\frac{\left ( t_1/2 \right )_3}{\left(t_1/2\right)_4}\right)^{n-1} }

\mathrm{ \frac{20}{10} \Rightarrow\left(\frac{60}{30}\right)^{n-1} }

\mathrm{ (2) \Rightarrow(2)^{n-1} }

\mathrm{ n-1=1 }

\mathrm{ n=2 }  [Second order w.r.t.[A] ]

\mathrm{ \text { So\, rate }=K[A]^2[B]^1}

Hence option 2 is correct.











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chirag

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