Diazonium salt decomposes as: C6H5N2CI -> C6H5Cl + N2. At 0°C, the evolution of N2 becomes two times faster when the initial concentration of the salt is doubled. Therefore, it is:

Explanation

The given reaction, Diazonium salt (C6H5N2Cl) decomposing into C6H5Cl (chlorobenzene) and N2 (nitrogen gas), follows the equation: C6H5N2Cl → C6H5Cl + N2. The question states that at 0°C, the evolution of N2 becomes two times faster when the initial concentration of the salt is doubled. Based on this information, let's analyze the possible options: a) A first-order reaction: In a first-order reaction, the rate of the reaction is directly proportional to the concentration of only one reactant. Doubling the initial concentration of the reactant would result in the rate becoming two times faster. This option seems plausible. b) Independent of the initial concentration of the salt: This option suggests that the rate of the reaction remains constant and doesn't change with changes in the initial concentration of the reactant. However, the given information contradicts this option, as it clearly states that doubling the initial concentration leads to a change in the reaction rate. c) A second-order reaction: In a second-order reaction, the rate of the reaction is proportional to the square of the concentration of a single reactant or the product of the concentrations of two reactants. The information provided doesn't seem to indicate a second-order reaction, as doubling the concentration of the salt wouldn't necessarily lead to the rate becoming two times faster. d) A zero-order reaction: In a zero-order reaction, the rate of the reaction is independent of the concentration of the reactants. Again, the given information contradicts this option, as it states that the rate becomes faster when the concentration of the salt is doubled. Based on the information provided, option a) "A first-order reaction" seems to be the most appropriate choice. Doubling the initial concentration of the salt leads to a doubling of the reaction rate, which is consistent with a first-order reaction.