Statement I: The rate law of a reaction is determined experimentally.
Statement II: The rate law of a reaction can be written from its balanced chemical equation.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Statement I is correct but Statement II is incorrect.
The rate law gives the rate of a reaction in terms of the molar concentrations of the reactants, each raised to some power (its order).
Statement I: The rate law of a reaction is determined experimentally. — True. The powers are found by measuring how the rate changes with concentration; they must be found by experiment.
Statement II: The rate law of a reaction can be written from its balanced chemical equation. — False. The exponents may or may not equal the stoichiometric coefficients. For the hydrolysis of ethyl acetate, \( \ce{CH3COOC2H5 + H2O -> CH3COOH + C2H5OH} \), both coefficients are 1, yet the rate law is Rate = k[CH3COOC2H5]1[H2O]0.
NCERT (2026-27 edition):
3.2.2 Rate Expression and Rate Constant – “… In these reactions, the exponents of the concentration terms are not the same as their stoichiometric coefficients. Thus, we can say that: Rate law for any reaction cannot be predicted by merely looking at the balanced chemical equation, i.e., theoretically but must be determined experimentally.”