zuai-logo
zuai-logo
  2. AP Chemistry
FlashcardFlashcardStudy GuideStudy Guide
Question BankQuestion Bank

Thermodynamic and Kinetic Control

Ethan Taylor

Ethan Taylor

7 min read

Listen to this study note

Study Guide Overview

This study guide covers kinetic control, explaining why spontaneous reactions (negative ΔG) can be slow. It reviews thermodynamics vs. kinetics, reaction rates, rate laws, and activation energy (Ea). The guide emphasizes the importance of Ea in determining reaction speed and uses the diamond-to-graphite conversion as a key example. Finally, it discusses how catalysts lower Ea, increasing reaction rates, and provides practice questions covering these concepts.

#Kinetic Control: Why Spontaneous Reactions Can Be Slow 🐌

Hey AP Chem student! Let's dive into why some reactions, even if they're supposed to happen, take forever. We're talking about kinetic control, a concept that's super important for understanding how reactions actually behave. Get ready to make some connections between thermodynamics and kinetics!

#Thermodynamics vs. Kinetics: A Quick Recap

Before we jump in, let's quickly review the difference between thermodynamics and kinetics:

  • Thermodynamics: Tells us if a reaction can happen (spontaneous/non-spontaneous). Think Gibbs Free Energy (ΔG).
  • Kinetics: Tells us how fast a reaction happens. Think reaction rates and activation energy.
Key Concept

It's crucial to remember that a negative ΔG (spontaneous reaction) doesn't guarantee a fast reaction! This is where kinetic control comes in.

#Brief Review of Kinetics

Okay, let's make sure we're all on the same page with kinetics. If you're feeling good, you can skim this, but a quick refresh never hurts!

  • Reaction Rate (R): How quickly reactants turn into products. It's measured as the change in concentration over time:

    • R=Δ[A]ΔtR = \frac{Δ[A]}{Δt}R=ΔtΔ[A]​ or R=−d[A]dtR = -\frac{d[A]}{dt}R=−dtd[A]​

  • Rate Laws: These equations relate reactant concentrations to the reaction rate:

    • R=k[A]n[B]mR = k[A]^n[B]^mR=k[A]n[B]m (where k is the rate constant, and n and m are reaction orders)

    • Example: If rate = k[A], the reaction rate depends directly on the concentration of A.

  • Activation Energy (Ea): The minimum energy needed for a reaction to occur. Think of it as the hill reactants need to climb to become products. ⛰️

    • Higher Ea = Slower reaction

    ![Activation Energy Diagram](https://zupay.blob.core.windows.net/resources/files/0baca4f69800419293b4c75aa2870acd_cf3c89_1661.png?alt=media&token=6d3fa74e-c878-48b4-a6da-296f...

Feedback stars icon

How are we doing?

Give us your feedback and let us know how we can improve

Question 1 of 8

🎉 Which of the following best describes what kinetics studies?

Whether a reaction is spontaneous

The rate of a reaction

The equilibrium of a reaction

The enthalpy change of a reaction