Question

Which of the following statements is not correct about order of a reaction?

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> AIPMT 2011 (PRE)

• A. The order of a reaction is always equal to the sum of the stoichiometric coefficients of reactants in the balanced chemical equation for a reaction
• B. The order of a reaction is the sum of the powers of molar concentration of the reactants in the rate law expression.
• C. The order of a reaction can be a fractional number
• D. Order of a reaction is experimentally determined quantity

Answer 1

The correct option is A The order of a reaction is always equal to the sum of the stoichiometric coefficients of reactants in the balanced chemical equation for a reaction

There are different orders for different reactions. It can be zero order, first order, second order, pseudo-first-order, etc
The exponent on each concentration term is the order of the reaction in that particular reactant
Since it is experimentally determined, it can be integers, fractions.
$2N_2{O}_5\to 4N{O}_2+O_2$
$\text{Rate}\left(r\right)=k\left[N_2{O}_5\right]$
It is a first-order reaction that is not equal to the stoichiometry of the reactants in a balanced chemical equation.
Now on checking the options, the order of a reaction can be a fractional number.
The order of a reaction is experimentally determined.
order is the sum of the powers to which the concentration of reactants is raised in a rate law expression.
Therefore, options A, B, and D have correct statements.
And option C is an incorrect statement.