Reaction Rate
Change in concentration per unit time: Rate = -d[A]/dt.
Example: If [N2O5] drops 0.160 to 0.140 M in 200 s, rate = 1.0e-4 M/s.
Adaptive
Learn Chemical Kinetics
Read the notes, then try the practice. It adapts as you go.When you're ready.
Session Length
~17 min
Adaptive Checks
15 questions
Transfer Probes
8
Lesson Notes
Chemical kinetics studies the rates of chemical reactions, factors influencing rates, and step-by-step mechanisms. The rate law relates reaction rate to reactant concentrations raised to experimentally determined powers. The Arrhenius equation connects rate constants to temperature and activation energy. Reaction mechanisms consist of elementary steps with the rate-determining step governing overall kinetics. Catalysts accelerate reactions by lowering activation energy.
This topic covers rate laws, integrated rate expressions, half-life calculations, the Arrhenius equation, collision theory, transition state theory, reaction mechanisms, intermediates, and catalysis for AP Chemistry Unit 5.
You'll be able to:
- Determine rate laws from experimental data using the method of initial rates
- Apply integrated rate laws and half-life calculations to predict concentration changes over time
- Use the Arrhenius equation to relate rate constants to temperature and activation energy
- Analyze reaction mechanisms to identify elementary steps, intermediates, and rate-determining steps
- Explain how catalysts accelerate reactions by lowering activation energy
One step at a time.
Interactive Exploration
Adjust the controls and watch the concepts respond in real time.
Key Concepts
Rate Law
Rate = k[A]^m[B]^n where exponents are experimental orders.
Example: 2NO+O2->2NO2: Rate=k[NO]^2[O2], third order overall.
Activation Energy
Minimum energy (Ea) for reaction; barrier to transition state.
Example: H2O2 decomposition: Ea ~75 kJ/mol uncatalyzed, ~8 with catalase.
Arrhenius Equation
k=Ae^(-Ea/RT) relates rate constant to T and Ea.
Example: ln k vs 1/T plot gives slope=-Ea/R.
Reaction Mechanism
Sequence of elementary steps; must match observed rate law.
Example: Slow step determines Rate=k[NO2][F2].
Catalyst
Lowers Ea via alternative pathway; not consumed; no equilibrium change.
Example: Pt/Pd in catalytic converters lower Ea for exhaust cleanup.
Half-Life
Time for [reactant] to halve. First-order: t1/2=0.693/k.
Example: C-14 half-life=5730 years regardless of starting amount.
Collision Theory
Reactions need collisions with energy >= Ea and proper orientation.
Example: Only properly oriented NO+O3 collisions with enough energy react.
Explore your way
Choose a different way to engage with this topic — no grading, just richer thinking.
Explore your way — choose one:
Concept Map
See how the key ideas connect. Nodes color in as you practice.
Worked Example
Walk through a solved problem step-by-step. Try predicting each step before revealing it.
Adaptive Practice
This is guided practice, not just a quiz. Hints and pacing adjust in real time.
Small steps add up.
What you get while practicing:
- Math Lens cues for what to look for and what to ignore.
- Progressive hints (direction, rule, then apply).
- Targeted feedback when a common misconception appears.
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