Lecture on Surface Area and Rate of Chemical Reactions

Introduction

Objective: Understand how the effective surface area of solid reactants affects the rate of chemical reactions.
Previous Video Recap: Explained rates of reaction using collision theory.
- Reactions occur when particles collide with sufficient energy.
- Rate determined by the frequency of successful collisions (number of successful collisions per second).

Solid Reactants and Collisions:
- Particles in solution can only react with particles on the solid's surface.
- Particles not on the surface cannot react.
Increasing Surface Area:
- Breaking a solid into smaller blocks increases surface area.
- More surface area allows more particles to react, increasing collision frequency and reaction rate.

Concept:
- Smaller solid blocks have a greater surface area to volume ratio than larger blocks.
- More particles on the surface lead to more collisions per second, increasing reaction rate.

Setup:
- Use marble chips (calcium carbonate) reacting with hydrochloric acid to produce CO₂ gas.
- Measure volume of CO₂ to determine reaction rate.
Measurement Tools:
- Measuring cylinder can be inaccurate due to rapid bubbling.
- Gas syringe provides more accurate results.
Alternative Method:
- Measure mass loss of CO₂ using a balance.
- Setup includes cotton-wool to allow CO₂ to escape but prevent acid splashing, which can cause anomalous results.

Key Learning: Solid reactants' surface area significantly affects the rate of chemical reactions.
Further Practice: Work on related questions available in the vision workbook for more understanding.

By the end of this session, you should be capable of describing how the surface area of solid reactants impacts the rate of chemical reactions.