An increase in the concentration of the reactants of a reaction leads to change in:

Solution & Explanation

\textbf{Answer:} (B) Collision frequency \textbf{Solution:} Increasing the concentration of reactants increases the number of reactant particles per unit volume, which increases the number of molecular collisions per unit time, i.e. the collision frequency. Threshold energy and activation energy depend on the nature of the reactants (the energy barrier) and are independent of concentration. The heat of reaction $\Delta H$ is a state function fixed by the reactants and products. Hence only the collision frequency changes.