Which of the following salts will form a basic solution

Which of the following salts will form a basic solution

Question
Name: ___________________
Chemistry 115
The quiz has 15 questions. You have 30 minutes.
The following equations might be useful:
[H+][-OH] = 1.0 x 10-14

pH = -log[H+]

For weak acids in water: Ka = [H+]2 / [HA]init
KaKb= 10-14 for a conjugate acid/base pair

[H+] = 10-pH

pH + pOH = 14

For weak bases in water: Kb = [-OH]2 /[Base]init
% ionization = [H+] / [HA]init x 100 %

1. Which of the following salts will form a basic solution?
a. NaBr
b. Ca(NO3)2
c. NH4Cl
d. NaCH3CO2
e. Al(ClO4)3

2. Which statement is true?
a. As the strength of a weak acid increases, the percent dissociation decreases
b. As the concentration of a weak acid increases, the percent dissociation
increases.
c. As the strength of a weak acid decreases, the percent dissociation increases.
d. The percent dissociation of a weak acid is independent of the identity of the
weak
acid.
e. As the value of Ka increases, the percent dissociation increases

3. Which list gives the acids in order of increasing strength?
a. CH4 < NH3 < H2S < H2O
b. NH3 < CH4 < H2O < H2S
c. H2S < PH3 < HCl < HBr
d. NH3 < PH3 < HI < HCl
e. NH3 < H2O < H2S < HBr

Consider the following acid-base reaction for the next three questions:
4. What is the Ka of the weak acid HClO2 if a 0.100 M solution of the acid has a pH = 2.22?
a. 3.6 x 10-4
b. 6.0 x 10-3
c. 1.6 x 10-3
d. 5.9 x 10-4
e. 1.3 x 10-

5. The equilibrium constant, K, for this reaction is 2.4×106 at 25 °C. Given that, which one of the
following statements is TRUE?
At equilibrium, the reaction mixture contains…
a. almost all CH3NH3+ and CH3CO2b. almost all CH3NH2 and CH3CO2H
c. equal amounts of CH3NH2, CH3CO2H, CH3NH3+ and CH3CO2d. the reaction mixture will be basic.
e. the reaction mixture will be acidic.

6. If the pH of a solution is increased by two (6 8), the proton concentration:
a. is decreased by a factor of 10.
b. is decreased by a factor of 100.
c. is increased by a factor of 10.
d. is increased by a factor of 100.
e. is decreased by a factor of 2
f. is increased by a factor of 2.

7. Which list gives equal concentrations of the following solutions in order of
decreasing acidity?
HC3H5O3 (Ka = 1.4 x 10-4) H2O (Ka = 1.0 x 10-14)
HCN (Ka = 4.9 x 10-10)

HCl (Ka = 2 x 106)

a. HC3H5O3 > HCl > HOCl > HCN > H2O
b. HCl > HC3H5O3 > HOCl > HCN > H2O
c. HCN > HOCl > HCl > HC3H5O3 > H2O
d. HCl > HC3H5O3 > HOCl > H2O > HCN
e. H2O > HCN > HOCl > HC3H5O3 > HCl

8. Which relationship between acid strengths is correct?
a. HClO4 > HF
b. H2O < -OH
c. HBr > HI

HOCl (Ka = 3.5 x 10-8)

d. NH3 > NH4+
e. HNO3 < HNO2

9. Label the acid, base, conjugate acid, conjugate base.

_______
_______

________

2

10. The pH of a 0.120 M phenol solution is (Ka of phenol = 1.3 x 10-10):
a. 1.000
b. 10.81
c. 11.11
d. 5.40
e. 4.48

11. The solution that will give a pH = 12.00 is (MW: NaOH = 40 g/mol):
a. 4.0 g NaOH in 1.0 L of solution.
b. 12 g NaOH in 1.0 L of solution.
c. 0.20 g NaOH in 2.0 L of solution.

d. 0.20 g NaOH in 0.50 L of solution.
e. 0.40 g NaOH in 0.10 L of solution

________

12. Which H3O+ concentration and classification (acidic vs. basic) are correctly matched for a
solution in which the OH- concentration is 5.6 x 10-6 M?
a. 5.6 x 10-6 M : basic
b. 5.6 x 10-6 M : acidic
c. 5.6 x 108 M : acidic
d. 1.8 x 10-9 M : basic
e. 1.8 x 10-9 M : acidic

13. Fill in the missing compounds in the following table of conjugate acid/base pairs.
Conjugate acid
H2CO3

Conjugate Base
NH2-

H3O

+

14. Based on the value of K given in question 5, what can be said about relative acid strengths?
a. CH3CO2H is a stronger acid than CH3NH2.
b. CH3NH3+ is a stronger acid than CH3CO2H.
c. CH3NH2 is a stronger acid than CH3CO2H.
d. CH3CO2H is a stronger acid than CH3NH3+.

15. Fill in the blanks:
According to the Brønsted definitions, an acid is a compound that _________ a proton and a
base is a compound that ________ a proton. An acid-base reaction involves transfer of a proton
from the _________ to the ________.
The answers in order are:

a. donates, accepts, base, acid

b. accepts, donates, base, acid

c. donates, accepts, acid, base

d. accepts, donates, acid, base