Question

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

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

Hint:

The order of a reaction is determined experimentally and is not necessarily related to the stoichiometric coefficients in the balanced chemical equation. It can be fractional or even zero for some reactions.

Answer 1

The Correct Option is B

Let’s evaluate each statement:

Statement (1): “The order of a reaction is the sum of the powers of molar concentration of the reactants in the rate law expression.”

This statement is correct. The order of a reaction is determined by the powers to which the concentration terms are raised in the rate law. The overall order is the sum of the individual exponents of the concentration terms of the reactants.

Statement (2): “The order of reaction is always equal to the sum of the stoichiometric coefficients of reactants in the balanced chemical equation of a reaction.”

This statement is incorrect. The order of a reaction is not necessarily equal to the sum of the stoichiometric coefficients in the balanced chemical equation. The order is an empirical quantity determined experimentally and often does not match the stoichiometric coefficients.

Statement (3): “The order of a reaction can be a fractional number.”

This statement is correct. The order of a reaction can be fractional, especially in complex reactions where the rate depends on reactant concentrations raised to non-integer powers.

Statement (4): “Order of a reaction is an experimentally determined quantity.”

This statement is correct. The order of a reaction is determined experimentally by studying how the reaction rate varies with reactant concentrations.

Thus, the incorrect statement is Statement (2), because the order of a reaction is not always equal to the sum of the stoichiometric coefficients in the balanced chemical equation.