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Methods of Determining Reaction Order MCQ - Practice Questions with Answers

Edited By admin | Updated on Sep 25, 2023 25:23 PM | #NEET

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Consider the Reaction \mathrm{A \rightarrow Products} the half life of a reaction at initial concentration \mathrm{0.1 \mathrm{~mol} L^{-1} \& \, 0.5 \mathrm{~mol} L^{-1}} are 200 sec and 40 sec respectively. The order of the reaction is

Consider a reaction \mathrm{ A \rightarrow Products}-having half -life 50 min- for a certain initial concentration. If the concentration of the reactions becomes doubled, the half-life of the reaction becomes \mathrm{ 100 \mathrm{~min}}.What is order of the reaction :

Consider a reaction
\mathrm{A \longrightarrow B}, having \mathrm{[A]_{0}^{2}\, t_{1 / 2}}  is constant. the order of the reaction is:

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Calculate the order of the reaction if 0.3 s and 0.6 s is the half life of two given samples. Also, initial concentration of the samples is 160 M and 80M respectively.

At 12.5 KPa and 800 K, a gaseous reaction had the half life period of 375 s. Find the order of the reaction, if the pressure is changed to 45 KPa

\mathrm{Co \sqrt{T}} was found to be constant in a single reactant reaction. Find the order of the reaction in which \mathrm{C_0} and T is the initial concentration of the reactant and half life, respectively. What is the order of the reaction?

For a reaction \mathrm{A^{\prime}(g) \longrightarrow B(g)} when volume of ron vessel reduce to half life become half. The order of reaction will be

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Consider a reaction \mathrm{A+B+C \rightarrow} Produce with the rate law Expression is

\mathrm{Rate \left.=k(A)^2 (B\right)^{-1}(C)^2}. The order of reaction ls:

Consider the reaction \mathrm{A+B+C\rightarrow } produced with ratelaw expression is Rate \mathrm{=k[A]^2[B ]^{\circ}[C]^{-1}} what will be the unit of rate constant (K) ?

 

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Concepts Covered - 3

How to Determine Order of Reaction: Half Life Method

It is used when the rate law involves only one concentration term.

\mathrm{t_{1 / 2} \propto(a)^{1-n}} 
or 
\mathrm{t_{1 / 2} \propto 1 / a^{n-1}}

For two different concentrations, we have:

\mathrm{\frac{\left(t^{1 / 2}\right)_{1}}{\left(t^{1 / 2}\right)_{2}}=\left(\frac{a_{2}}{a_{1}}\right)^{n-1}}

On taking logarithms on both sides, we get:

\mathrm{\log _{10} \frac{\left(t_{1 / 2}\right)_{1}}{\left(t_{1 / 2}\right)_{2}}=(n-1) \log _{10}\left(a_{2} / a_{1}\right)}

Hence,

\mathrm{n}=1+\frac{\log \left(\mathrm{t}^{1 / 2}\right)_{1}-\log \left(\mathrm{t}^{1 / 2}\right)_{2}}{\log \mathrm{a}_{2}-\log \mathrm{a}_{1}}
Here,  n is the order of the reaction.

How to Determine Order of Reaction: Graphical Method

Here graphs are plotted between rate and concentration to find the order of the reaction.

\left[\text {Rate }=\mathrm{k}(\text {concentration})^{\mathrm{n}}\right]

Plots of Rate vs Concentration

How to Determine Order of Reaction - Integrated Rate Law Method

If the data for time(t) and [A] is given then this method is applicable. Thus follows the steps given below to find the order of reaction by using the integrated rate law method.

  • Check for First Order: 
    1. Use the formula given below to find out the two values of k as k1 and k2.
      \mathrm{k\: =\: \frac{2.303}{t}\, log_{10}\left [ \frac{A_{o}}{A} \right ]}
    2. If these two values k1 and k2 are same, then this given reaction is of first-order. But if k1≠ k2, then check for zero-order.
  • Check for Zero-Order:
    1. Use the formula given below to find out the two values of k as k1 and k2.
      \mathrm{k\: =\: \frac{A_{o}-A}{t}}
    2. Again, if these two values k1 and k2 are same, then this given reaction is of zero-order. But if k1≠ k2, then check for second-order.
  • Check for Third-Order:
    1. Use the formula given below to find out the two values of k as k1 and k2.
      \mathrm{k\: =\: \frac{1}{t}\left [ \frac{1}{A}-\frac{1}{A_{o}} \right ]}
    2. Further, if these two values k1 and k2 are same, then this given reaction is of second-order. But if k1≠ k2, then check for third-order and so on.

Study it with Videos

How to Determine Order of Reaction: Half Life Method
How to Determine Order of Reaction: Graphical Method
How to Determine Order of Reaction - Integrated Rate Law Method

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