To determine which change would cause the greatest increase in the rate of the given reaction, we need to consider the factors that affect reaction rates: temperature and pressure.
1. Temperature Effects:
- Increasing the temperature generally increases the reaction rate. This is because higher temperatures provide more kinetic energy to the reacting molecules, leading to more frequent and more energetic collisions, which raises the probability of successful reactions.
- Conversely, decreasing the temperature generally decreases the reaction rate because the molecules have less kinetic energy, resulting in fewer and less energetic collisions.
2. Pressure Effects (for gaseous reactions):
- Increasing the pressure typically increases the reaction rate for reactions involving gases. This is because higher pressure means the gas molecules are closer together, leading to more frequent collisions.
- Decreasing the pressure has the opposite effect, as it causes the gas molecules to be more spread out, reducing the frequency of collisions.
Now, let's analyze each of the given options:
1. Decrease temperature and decrease pressure:
- Decreasing temperature decreases the rate.
- Decreasing pressure decreases the rate.
- Combined effect: Both factors decrease the reaction rate significantly.
2. Increase temperature and decrease pressure:
- Increasing temperature increases the rate.
- Decreasing pressure decreases the rate.
- Combined effect: One factor increases the rate while the other decreases it. The overall effect is uncertain without specific data but is not likely to cause the greatest increase.
3. Decrease temperature and increase pressure:
- Decreasing temperature decreases the rate.
- Increasing pressure increases the rate.
- Combined effect: One factor decreases the rate while the other increases it. Similar to option two, the overall effect is uncertain and not likely to be the greatest increase.
4. Increase temperature and increase pressure:
- Increasing temperature increases the rate.
- Increasing pressure increases the rate.
- Combined effect: Both factors work together to significantly increase the reaction rate.
Given the explanations and understanding of how temperature and pressure affect the rate of a reaction, the scenario that would likely cause the greatest increase in the reaction rate is to increase temperature and increase pressure.
Thus, the correct answer is:
4. Increase temperature and increase pressure
