Under what conditions will the rate of a chemical reaction always decrease?

The rate of a chemical reaction will always decrease under the following conditions:

1. Decrease in Concentration: The rate of a chemical reaction decreases as the concentration of the reactants decreases. This is because there are fewer particles available to react, which reduces the frequency of successful collisions.

2. Decrease in Temperature: Lowering the temperature slows down the molecules and reduces the number of successful collisions because the molecules have less kinetic energy. This results in a slower reaction rate.

3. Decrease in Surface Area: If a reactant is in a solid state, decreasing its surface area will reduce the rate of reaction. This is because there are fewer particles exposed and available to collide with other reactant particles.

4. Use of a Catalyst: If a catalyst is removed from a reaction, the rate of the reaction will decrease. Catalysts work by providing an alternative reaction pathway with a lower activation energy.

5. Increase in Activation Energy: If the activation energy of a reaction is increased, the rate of the reaction will decrease. This is because fewer particles will have the necessary energy to react when they collide.

6. Decrease in Pressure: For reactions involving gases, decreasing the pressure will decrease the rate of reaction. This is because the gas particles are further apart and collide less frequently.