Which of the following does not increase the number of particles of a substance available to react in a chemical reaction?
1) Increasing the temperature
2) Increasing the pressure
3) Decreasing the concentration
4) Increasing the concentration
The Correct Answer and Explanation is :
The correct answer is 3) Decreasing the concentration.
Explanation:
In chemical reactions, the rate at which reactants convert into products is influenced by several factors, including temperature, pressure, concentration, and the presence of catalysts. One of the fundamental principles governing these reactions is the collision theory, which states that for a reaction to occur, particles must collide with sufficient energy and proper orientation.
- Increasing the temperature: When the temperature of a substance is increased, the kinetic energy of its particles also increases. This means that the particles move faster and collide more frequently and with greater energy, leading to a higher likelihood of successful collisions that result in reactions. Therefore, increasing the temperature enhances the number of reactive collisions.
- Increasing the pressure: In reactions involving gases, increasing the pressure effectively decreases the volume available to the gas particles, causing them to be closer together. This results in more frequent collisions among the gas particles, thereby increasing the reaction rate. Thus, increasing the pressure raises the number of particles available to react.
- Decreasing the concentration: Concentration refers to the number of particles (molecules or ions) of a substance in a given volume. When the concentration of a reactant is decreased, there are fewer particles available to collide and react. This leads to a decrease in the frequency of effective collisions and, consequently, a lower reaction rate. Therefore, decreasing concentration does not increase the number of particles available to react; it actually reduces it.
- Increasing the concentration: Conversely, increasing the concentration of a reactant means there are more particles present in a given volume. This results in a higher frequency of collisions between reactant particles, leading to an increased reaction rate.
In summary, while increasing temperature, pressure, and concentration can enhance the number of reactive particles, decreasing concentration diminishes it, making option 3 the correct choice.