Quiz

QUIZ

1. In the Arrhenius definition of acids, what does the hydrogen ion become when an acid dissociates in solution?

a. H2O b. H3O+ c. H+ d. OH-

Answer: b. The H+ ion in an acid does not remain stable so that it combines with water to make a hydronium ion or H3O+ ion.

2. Which of the following is a base?

a. HSO4 b. HCl c. NH3 d. KCl

Answer: c. NH3 is a weak base because it is a proton acceptor, becoming NH4+.

3. What is the equilibrium constant for water?

a. 1 b. 1 x 1014 c. 1 x 10-7 d. 1 x 10-14

Answer: d. The equilibrium constant for water is 1 x 10-14, which is an important number because it is the product of the base constant times the acid constant for an acid and its conjugate base.

4. Which is considered a strong acid?

a. Perchloric acid b. Acetic acid c. Ammonium d. Formic acid

Answer: a. While it is difficult to remember all of these acids and bases, it is a good idea to remember as many of the strong bases and strong acids as possible. Each of these is a weak acid except for perchloric acid, which is a strong acid.

5. In understanding Lewis acids and bases, when these are combined, what do they form?

a. Bronsted-Lowry compounds b. Nucleophiles c. Adducts d. Electrophiles

Answer: c. In understanding the Lewis acid-base system, there are nucleophiles and electrophiles, which combine to make adducts, which are covalently bonded molecules that comprise these acids and bases combined.

6. The molecule Al(OH)3 or aluminum (III) hydroxide is an amphoteric molecule. What does this mean technically?

a. It is a strong acid b. It is a strong base c. It is a weak base d. It can be an acid or a base

Answer: d. Aluminum (III) hydroxide is considered amphoteric because it has the ability to act as an acid or a base depending on the environment it is placed in, based on the Lewis theory of acids and bases.

7. Which of the following molecules is a Bronsted-Lowry base but not an

Arrhenius base?

a. NH3 b. NaOH c. Ca(OH)2 d. KOH

Answer: a. While each of these is a base, only NH3 does not directly give an OH- ion to the solution, making it a Bronsted-Lowry base but not an Arrhenius base.

8. A weak acid and a weak base are involved in a neutralization reaction. What will the pH be at the time of neutralization?

a. 7 b. Less than 7 c. Greater than 7 d. It depends on the Ka and Kb

Answer: d. This pH will be different depending on these K constants. If the Ka is greater, the pH will be less than 7; if the Kb is greater, the pH will be greater than 7.

9. Which is not an example of a buffer system?

a. Ammonia b. Acetate c. Sulfuric acid/sodium sulfate d. Phosphate

Answer: c. With the exception of sulfuric acid/sodium sulfate, each of these is a buffer system because it is a system involving a weak acid or weak base plus the corresponding salt. Sulfuric acid and sodium sulfate together involve strong acids and salt solutions, which would not make a very good buffer system.

10. If the H+ concentration is 0.00001 M/l, what is the pH?

a. 3 b. 4 c. 5 d. 6

Answer: c. The pH is the negative log of the hydrogen concentration. A concentration of 0.00001 M/l is 10 to the -5 power, the negative log of which is 5.