The rate of chemical reaction of solids are not affected by

Step 1: Analyze the question We are asked which factor does NOT affect the rate of reactions involving solids.

Step 2: Explain the concept Reaction rate depends on how often and how effectively particles collide. The main factors are:

• Catalyst: provides an alternative pathway with lower activation energy, so it speeds up reactions (including those involving solids, e.g. MnO₂ in the decomposition of KClO₃).
• Particle size (surface area): smaller particles expose more surface, so there are more collisions and a faster reaction. This is very important for solids.
• Temperature: higher temperature gives particles more kinetic energy, so more collisions have enough energy to react. This affects all reactions.
• Pressure: pressure only matters significantly for gases, because it changes their concentration by squeezing particles closer together. Solids (and liquids) are almost incompressible, so pressure changes do not noticeably change their reaction rate.

Step 3: Solve

• A. Catalyst: affects the rate, so not the answer.
• B. Pressure: has negligible effect on solids, so this is the answer.
• C. Particle size: affects the rate, so not the answer.
• D. Temperature: affects the rate, so not the answer.

Step 4: Answer The correct option is B. pressure.

Exam tip: Remember "Pressure is for gases only." If a question involves solids or liquids only, pressure is usually the factor that makes no difference. For solids, think surface area (particle size), temperature, concentration (for solutions), and catalyst.