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AP chem unit 6 cram
1. Kinetics Basics
Q: What is the definition of kinetics?
A: The study of the speed (rate) of chemical reactions and the factors affecting it.
Q: How is the reaction rate represented on a graph?
A: The slope of the graph of concentration vs. time shows the speed of the reaction.
Q: How does the rate change during a reaction?
A: Reaction rates decrease over time as reactant concentrations drop.
2. Collision Theory
Q: What does collision theory state?
A: For a reaction to occur, reactant particles must collide with enough kinetic energy and proper orientation.
Q: What is the difference between effective and ineffective collisions?
A:
• Effective collisions: Form products by breaking bonds.
• Ineffective collisions: Do not result in product formation.
Q: What is activation energy (Ea)?
A: The minimum energy required for reactants to form an activated complex and proceed to products.
Q: How do catalysts affect a reaction?
A: Catalysts lower activation energy, increasing reaction rate by providing an alternative pathway.
3. Dynamic Equilibrium
Q: What is dynamic equilibrium?
A: A state where the rate of the forward reaction equals the rate of the reverse reaction, with no net change in concentrations of reactants and products.
Q: Are the amounts of reactants and products equal at equilibrium?
A: No, the amounts may differ, but their concentrations remain constant over time.
4. Equilibrium Constants (Kc and Kp)
Q: How is calculated?
A:
Q: How is calculated for gases?
A:
Q: What is the relationship between and ?
Where .
5. Q vs. K and Reaction Direction
Q: What does the reaction quotient (Q) indicate?
• : Reaction shifts right (forward).
• : System is at equilibrium.
• : Reaction shifts left (reverse).
6. Le Chatelier’s Principle
Q: What happens when a system at equilibrium is disturbed?
A: It shifts in the direction that counteracts the disturbance.
Q: How do concentration changes affect equilibrium?
• Increase reactant concentration: Shift right (forward).
• Increase product concentration: Shift left (reverse).
Q: How does temperature affect equilibrium in exothermic and endothermic reactions?
• Exothermic ():
• Increase temp → shift left, decreases.
• Decrease temp → shift right, increases.
• Endothermic ():
• Increase temp → shift right, increases.
• Decrease temp → shift left, decreases.
Q: What happens when pressure changes?
• Decrease volume → shift to fewer moles of gas.
• Increase volume → shift to more moles of gas.
7. ICE Table Method
Q: What are the steps for solving equilibrium problems using an ICE table?
1. Write the initial concentrations/pressures.
2. Use stoichiometry to represent changes as .
3. Write expressions for equilibrium concentrations.
4. Substitute into the or expression.
5. Solve for and calculate concentrations.
8. Common Ion Effect
Q: What is the common ion effect?
A: When an ion common to a reaction is added from an external source, equilibrium shifts to reduce the concentration of that ion.
Q: How does the common ion effect shift equilibrium?
A: Adding a common ion shifts equilibrium toward the side that consumes that ion.
9. Reaction Rate Laws
Q: What is the general rate law?
Where and are reaction orders determined experimentally.
Q: What are the characteristics of zero, first, and second-order reactions?
• Zero order: Rate is independent of concentration.
• First order: Rate is directly proportional to concentration.
• Second order: Rate is proportional to the square of concentration.
10. Simplifying Approximations
Q: When is it valid to approximate as 1.0?
A: When is very small and is much smaller than the initial concentration. Ensure the ratio .
11. Key FRQ Tips
Q: What is the difference between “Explain,” “Justify,” and “Why” in FRQs?
• Explain: Provide reasoning and evidence.
• Justify: Use evidence to support your reasoning.
• Why: Focus on the reasoning behind a process.
