Chemistry: Kinetics & Chemical Equilibrium Flashcards
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Read the first 7 Chemistry: Kinetics & Chemical Equilibrium flashcards as text
For the reaction rate = k[A]^2[B], what happens to the rate if [A] is tripled while [B] is held constant?
Answer: Rate increases 9x
Since A is second order, tripling [A] gives 3^2 = 9 times the rate.
A reaction is first order in a reactant with a half-life of 20 seconds. How much of the reactant remains after 60 seconds?
Answer: 1/8
60 seconds is three half-lives, so (1/2)^3 = 1/8 remains.
Which statement about a catalyst is correct?
Answer: It lowers the activation energy of both forward and reverse reactions
A catalyst provides a lower-energy pathway, speeding both directions equally without changing K.
For a first-order reaction, which plot yields a straight line?
Answer: ln[A] versus time
A first-order integrated rate law gives a linear plot of ln[A] versus time.
The rate constant k of a reaction increases with temperature primarily because
Answer: more molecules have energy exceeding the activation energy
Higher temperature raises the fraction of collisions with sufficient energy to react.
In the Arrhenius equation k = A·e^(-Ea/RT), a larger activation energy Ea results in
Answer: a smaller rate constant
A larger Ea makes the exponential term smaller, decreasing k.
Units of the rate constant k for a second-order reaction are
Answer: M^-1·s^-1
Second-order rate constants have units of M^-1·s^-1.