Statement I: The rate law equation can be found only by experiment

Statement II: It can be written from the stoichiometric equation

Statement I is true but statement II is false

The correct answer is option 3. Statement I is true but statement II is false.

Let us break down why each statement is true or false:

Statement I: The rate law equation can be found only by experiment.

Rate Law: The rate law of a reaction describes how the rate of the reaction depends on the concentration of reactants. It has the form:

\(\text{Rate} = k[A]^m[B]^n\)

where \( k \) is the rate constant, \( [A] \) and \( [B] \) are the concentrations of reactants, and \( m \) and \( n \) are the reaction orders with respect to each reactant.

Experimental Determination: The rate law cannot be predicted solely from the balanced chemical equation. To determine the rate law, one must conduct experiments to measure how the reaction rate changes as the concentrations of reactants are varied. This experimental data helps to determine the values of \( k \), \( m \), and \( n \).

Reason: The rate law is related to the reaction mechanism, which may not be apparent from the balanced equation alone. Thus, experimental data is essential for determining the correct rate law.

Statement II: It can be written from the stoichiometric equation.

Stoichiometric Equation: The balanced chemical equation provides the stoichiometric coefficients of the reactants and products, which are related to the amounts of substances involved in the reaction.

Rate Law: The reaction order in the rate law (exponents in the rate law) does not necessarily match the stoichiometric coefficients of the reactants. For example, in some complex reactions, the rate law is determined by the mechanism of the reaction, which may involve intermediates or steps that are not directly reflected in the overall balanced equation.

Reason: The stoichiometric coefficients give the mole ratios but do not provide the information about the actual reaction order. Therefore, the rate law must be experimentally determined.

Summary:

Statement I is correct because the rate law must be found experimentally through observations and measurements.

Statement II is incorrect because the stoichiometric equation alone cannot provide the rate law. Experimental data is required to accurately determine the rate law.