Chemical Kinetics — Important Questions

Temperature, Concentration of reactants, Presence of catalyst, Pressure (for gaseous reactions)

Temperature increases molecular kinetic energy, concentration affects collision frequency, catalysts provide alternate pathways with lower activation energy, and pressure affects concentration of gases. Molecular weight of products does not directly affect reaction rate.

It is always a whole number, It is defined only for elementary reactions, It represents the number of molecules participating in an elementary reaction

Molecularity is always a positive integer (1, 2, or 3) representing the number of molecules that must collide simultaneously in an elementary reaction. It cannot be zero or fractional, unlike order of reaction.

Remain the same

For first-order reactions, t₁/₂ = 0.693/k, which is independent of initial concentration. This is a characteristic property of first-order reactions - their half-life remains constant.

Sufficient kinetic energy (threshold energy), Proper orientation of molecules

Effective collisions require two main conditions: molecules must have kinetic energy equal to or greater than the threshold energy, and they must collide with proper orientation to facilitate bond breaking and formation.