Which one of the following factors would NOT speed up a chemical reaction?

• A. Decreasing the temperature
• B. Increasing the surface area of a solid reactant
• C. Adding a catalyst
• D. Increasing the concentration of reactants

Answer: (A)

Verified step by step guidance

1. Understand that the rate of a chemical reaction depends on factors that increase the frequency or energy of collisions between reactant molecules.
2. Recall that increasing the surface area of a solid reactant exposes more particles to react, which increases the collision frequency and speeds up the reaction.
3. Know that adding a catalyst provides an alternative reaction pathway with a lower activation energy, which increases the reaction rate without being consumed.
4. Recognize that increasing the concentration of reactants raises the number of particles in a given volume, leading to more frequent collisions and a faster reaction.
5. Understand that decreasing the temperature reduces the kinetic energy of molecules, leading to fewer collisions with sufficient energy to overcome the activation barrier, thus slowing down the reaction.