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Order of Reaction - Practice Questions & MCQ

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

Quick Facts

  • Important Points About Order of Reaction is considered one the most difficult concept.

  • 33 Questions around this concept.

Solve by difficulty

For the reaction A+2B\rightarrow C, rate is given by R=\left [ A \right ]\left [ B \right ]^{2}  then the order of the reaction is

Which one of the following statements for the order of a reaction is incorrect?

The Energy profile diagram for an elementary reaction consist of:

 A reaction is said to be elementary if:

Consider the chemical reaction A \rightarrow B, it is if observed that reaction rate becomes double if we increases the conc. of A by four times.The order of reaction with respect to 'A' is.

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Consider the reaction: \mathrm{I}^{-}+\mathrm{OC}^{-} \rightarrow \mathrm{IO}^{-}+\mathrm{Cl}^{-} in concious medium, the rate of the reaction is given by \mathrm{\frac{d\left[I^{-7}\right]}{d t}=\frac{k[I]\left[\mathrm{O}^{-}\right]}{[\mathrm{OH}]}}, the overall order of the reaction is


Following data is obtained by student in the decomposition of gas.

\mathrm{P(mmHg)} 50 100 200 400



\mathrm{8} \mathrm{2} \mathrm{0.1} \mathrm{0.02}

The Order of Reaction is 

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For a reaction \mathrm{A \rightarrow P}, when initial concentration of reactant half life becomes 3 times. The order of reaction will be

For a reaction \mathrm{A+B \rightarrow P} when concentration of A doubled, rate becomes 4 times and when concentration of A and B both doubled rate becomes doubled. Find the order of the reaction

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The concentration of reactant undergoing decomposition was 1,0.8, 0.67 \mathrm{~molL}^{-1}after 1,2 and 3 minutes respectively. The order of reaction is

Concepts Covered - 3

Important Points About Order of Reaction

Order of reaction is defined as the number of reactants which determine the rate of reaction. In other words, it is the sum of exponents raised on active masses of reactants in a rate law equation.
Let us consider this reaction
Rate law equation for the reaction can be given as:

               \begin{array}{l}{\mathrm{R} \propto[\mathrm{A}]^{p}[\mathrm{B}]^{q}} \\\\ {\mathrm{R}=\mathrm{K}[\mathrm{A}]^{\mathrm{p}}[\mathrm{B}]^{\mathrm{q}}}\end{array}
\text { Order of reaction }=\mathrm{p}+\mathrm{q}
Rate constant and order for various reacting species is an experimental finding and cannot be predicted directly from the stoichiometry of the balanced reaction.

  1. It is an experimental value.

  2. It may be zero, negative or in fraction.

  3. Order of reaction depends upon temperature, pressure and concentration etc.

  4. It determines rate of reaction.

  5. Order of reaction is determined by the slowest step of the reaction.

  6. High order reactions are rare due to less chance of effective collisions between molecules.

  7. Anything in excess is not counted in order of the reaction. Example, in hydrolysis of ester and sugar water is in excess so it is neglected for order.

Simple/Elementary Single Step Reaction
  • In comple reaction there are many steps. Among those only one step is rate-determining step as it is a slow reaction.
  • The order of the reaction can be found out using the stoichiometric coefficients of the rate-determining step or the slowest step.
  • In simple reaction, the reaction completes in one single step and that is the rate-determining step. For simple reactions, Gulberg and waage law of mass action is valid.
    For example:
    \mathrm{H_{2}\: +\: I_{2}\rightarrow 2HI}
    Since it is a simple reaction, thus the rate of reaction is given as:
    \mathrm{Rate\: =\: K[H_{2}]^{1}[I_{2}]^{1}}
Initial Rate Method to Determine Correct Rate Law and Order of Reaction

Consider the reaction:

\mathrm{2A\: +\: B\: \rightarrow P}

The rate law for this reaction is given as follows:

\mathrm{Rate\: =\: K[a]^{x}[B]^{y}}

Now, x and y are the coefficients that are determined experimentally.

K = Rate constant
x,y = Order of reaction with respect to A and B.

Study it with Videos

Important Points About Order of Reaction
Simple/Elementary Single Step Reaction
Initial Rate Method to Determine Correct Rate Law and Order of Reaction

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