Which of the following factors does NOT affect the rate of reaction?

The rate of a chemical reaction is influenced by several factors, including the concentration of reactants, the presence of a catalyst, and the temperature. Each of these elements plays a crucial role in determining how quickly a reaction occurs.

Concentration of reactants affects the frequency of collisions between particles; higher concentrations generally lead to more collisions, thereby increasing the reaction rate. Similarly, temperature impacts kinetic energy; at higher temperatures, particles move faster and collide more frequently and with greater energy, leading to an increased rate of reaction. Catalysts provide an alternative pathway for a reaction to occur with a lower activation energy, thus speeding up the reaction without being consumed in the process.

On the other hand, while the cost of reactants may influence the economic feasibility of a reaction or a process, it does not directly impact the kinetic or mechanistic aspects of how fast the reaction proceeds. Therefore, this factor does not affect the rate of reaction in the scientific context of chemistry. Thus, the assertion that the cost of the reactants does not affect the reaction rate is correct.