Cracking the SAT Chemistry Subject Test

CHAPTER 11 ACIDS AND BASES

Drill 1

1. B Litmus is an indicator that is blue in basic solutions. Since NH 3 is
   the most obvious base among the choices, the answer is (B).


2. B At 25°C, a pH greater than 7 indicates a basic solution. (B) is
   correct.


3. C A nonelectrolyte does not dissociate into ions in water. Soluble
   ionic compounds, strong acids, and strong bases are all strong electrolytes,
   so eliminate (A) (a strong acid). Weak acids and bases ionize to a slight
   extent, and, therefore, are weak electrolytes. So eliminate (B) (weak base)
   and (D) and (E) (both weak acids). What’s left? Water. But doesn’t water
   ionize to a slight extent? Yes, but check out how slightly: Kw(equilibrium
   constant for the ionization of water) at 25°C is 1.0 × 10−14. That’s so small
   that we can consider water to be a nonelectrolyte. (C) is correct.


4. A The same species that makes strong electrolytes (soluble ionic
   compounds, strong acids, and strong bases) has an ionization reaction that
   essentially goes to completion. Are any of these answer choices strong
   acids or bases? Yes. HBr is a strong acid. It completely ionizes into H+ and
   Br− ions in water, so (A) is correct.


5. F, T Divide and conquer! Look at statement I by itself, and decide if it’s
   true or false. It’s false. If you add an acid to neutral water you
   increase the hydrogen ion concentration and decrease the hydroxide
   ion concentration.
   Is the second statement true or false? This is a true
   statement about water’s ion product. So, statement I is
   false, and statement II is true.


6. F, F Remember the six common strong acids? HI is one of them, so
   statement I is false.