The speed of a reaction is influenced by:

The speed of a reaction, or its rate, is influenced by several factors, among which the activation energy and the concentration of reactants play critical roles.

Activation energy is the minimum energy required for a reaction to occur. A lower activation energy generally results in a faster reaction, as more reactant molecules can achieve the necessary energy threshold to transform into products. This is why enzymes, which lower the activation energy of biochemical reactions, are crucial in biological systems—they significantly enhance reaction rates.

Similarly, the concentration of reactants also affects the reaction rate. According to the principles of chemical kinetics, an increase in the concentration of reactants typically increases the likelihood of collisions between reactant molecules. More collisions lead to a higher probability of reaction events occurring over a given time, thereby increasing the overall rate of product formation.

Combining both concepts, the activation energy dictates how easily a reaction can occur, while the concentration of reactants influences how often the reactants are able to collide and react. Therefore, the speed of a reaction is determined by both the activation energy and the concentration of reactants, making the selection accurate.