To determine which action is likely to decrease the rate of the reaction when a cube of manganese oxide is added to a solution of hydrogen peroxide, let's analyze each option:
1. Using a larger amount of solution:
- Increasing the volume of hydrogen peroxide solution might dilute the concentration of manganese oxide, but overall, it generally does not significantly slow down a reaction.
2. Increasing the mass of the cube:
- Adding more manganese oxide would usually increase the rate of the reaction because more catalyst is available for the reaction to proceed more quickly.
3. Chilling the hydrogen peroxide solution:
- Lowering the temperature of a reaction typically decreases the reaction rate because it reduces the kinetic energy of the molecules involved, leading to fewer collisions and lower chances of successful reactions.
4. Smashing the cube into pieces:
- Breaking the cube into smaller pieces increases the surface area of manganese oxide that is in contact with the hydrogen peroxide. This would increase the rate of reaction because more catalyst surface area is available for the reaction.
Given the options, the action that is most likely to decrease the rate of the reaction is:
Chilling the hydrogen peroxide solution.
This is because lowering the temperature generally reduces the kinetic energy of molecules, leading to fewer effective collisions and thus a slower reaction rate.
