Cracking the SAT Chemistry Subject Test

CHAPTER 10 KINETICS AND EQUILIBRIUM

Drill 1

1. E While the surface area of solids and liquids can be increased
   (through crushing a solid or spraying a liquid), the surface area of gases
   cannot. Which answer choice has solid or liquid reactants? Choice (E) does,
   and it’s the correct answer.


2. B When the volume of a system is decreased, equilibrium will shift in
   the direction that produces fewer moles of gas. Eliminate (A) and (E)—
   neither reaction involves a gaseous species, so pressure changes will not
   affect their equilibrium. Now, look at the other three choices: Which
   reaction involves fewer moles of gas on the right than on the left? Choice
   (B) does (3 moles on the left, and 2 on the right). So the correct answer is
   (B).


3. A We’re asked about reverse reactions, so read choices (A) to (E)
   from right to left. Recall that only gaseous and aqueous species can have
   their concentration increased. Choices (B), (C), (D), and (E) have either a
   gaseous or aqueous species on the right side (this is a bit tricky—these
   would be the reactants of the reverse reaction). That leaves A, which has a
   single solid reactant for its reverse reaction. The concentration of pure
   solids cannot be changed, so (A) is correct.


4. F, T Divide and conquer! Assess the first statement by itself. Is it true or
   false? If you increase the concentration of a product, equilibrium
   shifts in the direction that creates more reactant, so in this case, to the
   left. This means that we will see an increase, not a decrease, in the
   concentration of reactants. The statement is false.
   What about the second statement? It is a statement of
   Le Chatelier’s principle, so it’s true. The first statement
   is false, and the second is true.


5. F, F Divide and conquer. Is the first statement true or false? Don’t be