Higher Chemistry: Unit 3 - Controlling the Rate: Factors Effecting Rate

Summary

This chemistry tutorial dives into the factors that control the rate of a reaction, focusing on particle size, concentration, temperature, and catalysts. It explains how successful collisions drive reaction rates and explores kinetic energy distribution curves. The video also clarifies how catalysts lower activation energy and enhance reaction speed without altering the energy of particles. Finally, the video covers relative rate calculations, experimental design tips, and the impact of temperature and concentration on reaction rates, providing a comprehensive guide for understanding these key concepts in chemistry.

Takeaways

• 😀 Successful collisions are key to increasing the rate of a reaction. Particles must collide with sufficient energy and correct geometry.
• 😀 Larger particles with a smaller surface area result in fewer successful collisions and a slower reaction rate.
• 😀 Higher concentration increases the number of particles, leading to a higher rate of successful collisions and an increased reaction rate.
• 😀 Increasing temperature gives particles more kinetic energy, increasing the number of successful collisions and thus the reaction rate.
• 😀 Lowering the temperature reduces the number of particles with sufficient energy to overcome activation energy, leading to a slower reaction rate.
• 😀 Energy distribution curves illustrate how temperature changes the number of particles that can overcome activation energy, shifting the curve to the right with increased temperature.
• 😀 Catalysts increase the reaction rate by lowering the activation energy. They provide an alternative reaction pathway but are not used up in the process.
• 😀 Relative rate is calculated as 1 divided by the time taken for the reaction to occur (in seconds), and is always expressed per second.
• 😀 Increasing concentration typically results in a linear increase in reaction rate, whereas increasing temperature causes an exponential increase in reaction rate.
• 😀 When conducting experiments, ensure equipment is dry to maintain accurate concentrations, and for temperature experiments, use a hot water bath for more controlled heating.
• 😀 In experimental design, maintaining constant volume and adjusting water content in solutions can help control concentration without affecting the total volume.

Q & A

What are the two main factors that determine whether a collision between particles will result in a successful reaction?

The two main factors are: 1) The particles must collide with sufficient energy to overcome the activation energy, and 2) The particles must collide with the correct geometry.

How does particle size affect the rate of a reaction?

Smaller particles have a larger surface area, which increases the number of successful collisions, leading to a higher reaction rate. Larger particles have a smaller surface area, which reduces the number of collisions and therefore slows down the reaction rate.

What effect does concentration have on the rate of a reaction?

Higher concentration increases the number of particles in the same volume, resulting in a higher probability of successful collisions and thus a faster reaction rate. Lower concentration results in fewer particles and a slower reaction rate.

How does temperature affect the rate of a chemical reaction?

Increasing temperature gives particles more kinetic energy, allowing more particles to have sufficient energy to overcome the activation energy. This increases the number of successful collisions and accelerates the reaction rate. Lower temperature has the opposite effect.

What does the kinetic energy distribution curve represent, and how does it change with temperature?

The kinetic energy distribution curve represents the number of molecules at different energy levels. When temperature increases, the curve shifts to the right, showing that more molecules have sufficient energy to overcome the activation energy. When temperature decreases, the curve shifts to the left.

What is the role of catalysts in a chemical reaction?

Catalysts increase the reaction rate by lowering the activation energy. They do this by providing an alternative reaction pathway. Catalysts are not consumed in the reaction and can be used repeatedly.

How does a catalyst lower the activation energy on a reaction pathway diagram?

A catalyst lowers the activation energy by shifting the activation energy curve downward on a reaction pathway diagram, allowing more particles to have sufficient energy to react.

What is the formula to calculate the relative rate of a reaction?

The relative rate is calculated as one divided by the time the reaction took in seconds. The formula is: Relative rate = 1 / Time (seconds).

How does concentration affect the relative rate of a reaction, and what type of relationship is expected?

Concentration typically affects the rate via a linear relationship. Doubling the concentration usually doubles the rate, meaning the relative rate increases directly with concentration.

How does temperature affect the relative rate of a reaction, and what type of relationship is observed?

Temperature affects the relative rate exponentially. A small change in temperature can cause a significant increase in the rate, as more particles will have enough energy to overcome the activation energy.