Kinetics and equilibrium flashcards

Kinetics describes how fast a chemical reaction occurs, while equilibrium describes the state where forward and reverse reaction rates are equal. Students must understand reaction rate laws, rate constants, reaction orders determined experimentally, and how activation energy relates to reaction speed. The Arrhenius equation connects temperature to the rate constant. For equilibrium, students need to master writing equilibrium expressions (Keq, Kc, Kp), interpreting the magnitude of K, and applying Le Chatelier's principle to predict how systems respond to stress. The reaction quotient Q helps determine which direction a reaction will shift to reach equilibrium. Students must also understand how catalysts affect kinetics without changing equilibrium position, and how energy diagrams illustrate activation energy and the effect of catalysts on reaction pathways.

1. Card 1

   What is the rate law for a reaction, and how is it determined?

   The rate law expresses rate as k[A]^m[B]^n. Reaction orders m and n are determined experimentally from data, not from the balanced equation.

2. Card 2

   What does the rate constant k tell you about a reaction?

   The rate constant k is specific to a reaction at a given temperature. A larger k means a faster reaction. k changes with temperature but not with concentration.

3. Card 3

   How do you determine the overall reaction order?

   The overall reaction order is the sum of all individual exponents in the rate law. For rate = k[A]^2[B]^1, the overall order is third order.

4. Card 4

   What is the Arrhenius equation and what does it show?

   The Arrhenius equation is k = Ae^(-Ea/RT). It shows that as activation energy Ea decreases or temperature T increases, the rate constant k increases.

5. Card 5

   What is activation energy?

   Activation energy (Ea) is the minimum energy colliding particles must have for a reaction to occur. Higher Ea means a slower reaction at a given temperature.

6. Card 6

   How does a catalyst affect a reaction?

   A catalyst lowers the activation energy by providing an alternative reaction pathway. It speeds up the reaction but does not change the equilibrium constant or the overall energy change.

7. Card 7

   What does it mean when a reaction is at equilibrium?

   At dynamic equilibrium, the forward and reverse reactions occur at equal rates. Concentrations of reactants and products remain constant but are not necessarily equal.

8. Card 8

   How do you write an equilibrium expression Kc?

   Kc equals the product of product concentrations raised to their stoichiometric coefficients divided by reactants raised to theirs. Pure solids and liquids are excluded.

9. Card 9

   What does the magnitude of K tell you about a reaction?

   A large K (much greater than 1) means products are favored at equilibrium. A small K (much less than 1) means reactants are favored at equilibrium.

10. Card 10

    What is the reaction quotient Q and how is it used?

    Q is calculated like K but using current concentrations. If Q < K, the reaction shifts forward; if Q > K, it shifts in reverse to reach equilibrium.

11. Card 11

    State Le Chatelier's principle.

    Le Chatelier's principle states that if a system at equilibrium is disturbed, it will shift in the direction that partially counteracts the stress and restores equilibrium.

12. Card 12

    How does temperature change affect K?

    Unlike concentration or pressure changes, temperature changes alter the value of K itself. For an exothermic reaction, increasing temperature decreases K, favoring reactants.

• Students often assume reaction orders can be read directly from the coefficients in the balanced equation, but they must always be determined from experimental rate data.
• A common error is thinking that adding a catalyst shifts the equilibrium position or changes the value of K, when in fact it only helps the system reach equilibrium faster.
• Many students confuse Q and K, forgetting that Q uses current non-equilibrium concentrations and that comparing Q to K is what tells you the direction of the shift, not just whether products or reactants are present in excess.

Planning your revision? Read how to revise AP Chemistry, or make cards from your own notes with the notes to flashcards tool.