Chemistry Practice Exam 2
1. Which species are acting as Brønsted acids in the reaction below ?
HSO4-(aq) + H2O(l)
D H3O+(aq) + SO42- (aq)a) H2O
b) H2O and H3O+
c) H2O and SO42-
d) HSO4- and H3O+
e) HSO4- and SO42-
2. Which molecule is a STRONG acid?
a) HF
b) H2SO4
c) H3BO3
d) HCO2H
e) CH3COOH
3. Which set is NOT a conjugate acid/base pair?
|
|
Acid |
Conjugate Base |
|
a) |
HS- |
S2- |
|
b) |
NH4+ |
NH3 |
|
c) |
HNO3 |
NO3- |
|
d) |
H2O |
H3O+ |
|
e) |
H2PO4- |
HPO42- |
4. What is the equilibrium concentration of OH- in a solution that has a pH = 6.25?
a) 8.9 x 10-1 M
b) 8.0 x 10-1 M
c) 5.6 x 10-7 M
d) 1.0 x 10-7 M
e) 1.8 x 10-8 M
5. Which equation correctly describes the relationship between Kb & Ka for a conjugate acid/base pair ?
a) Kb = Kw x Ka
b) Kb = Ka / Kw
c) Kb = Kw / Ka
d) Kb = Kw + Ka
e) Kb = Kw - Ka
6. Which acid would have the STRONGEST conjugate base?
|
a) |
HIO3 |
Ka = 0.16 |
|
b) |
HC2O4- |
Ka = 5.4 x 10-5 |
|
c) |
HOClO3 |
Ka = 1 x 108 |
|
d) |
H3AsO4 |
Ka = 6.0 x 10-3 |
|
e) |
C6H5OH |
Ka = 1.0 x 10-10 |
7. What is the Ka of the weak acid phenylacetic acid, C6H5CH2COOH, if 2.1 % of the acid dissociates in a 0.12 M solution ?
a) 5.2 x 10-5
b) 3.7 x 10-5
c) 2.1 x 10-2
d) 1.8 x 10-1
e) 3.7 x 101
8. What is the pH of a 0.020 M citric acid , H3C6H8O7, solution ?
citric acid: Ka = 7.5 x 10-4
a) 1.6
b) 2.2
c) 3.1
d) 3.7
e) 4.4
9. What is the correct ranking of bases in order of increasing basic strength?
|
Hydrazine (H2NNH2) |
pyridine (C5H5NH) |
bicarbonate ion (HCO3-) |
|
Kb = 1.2 x 10-6 |
Kb = 1.7 x 10-9 |
Kb = 2.2 x 10-8 |
a) bicarbonate ion < hydrazine < pyridine
b) bicarbonate ion < pyridine < hydrazine
c) hydrazine < pyridine < bicarbonate ion
d) pyridine < hydrazine < bicarbonate ion
e) pyridine < bicarbonate ion < hydrazine
10. The lining of the stomach contains cells that secrete a solution of HCl. Which drink would best alleviate heartburn (excess acid in the stomach) ?
|
a) |
milk |
pH = 6.5 |
|
b) |
wine |
pH = 3.8 |
|
c) |
diet soda |
pH = 4.3 |
|
d) |
apple juice |
pH = 3.0 |
|
e) |
milk of magnesia |
pH = 10.5 |
11. What is the concentration of OH- ion in a 1.5 M solution of CH3NH2, a weak base?
CH3NH2: Kb = 4.8 x 10-4
a) 2.2 x 10-2 M
b) 2.7 x 10-2 M
c) 8.1 x 10-2 M
d) 3.6 x 10-4 M
e) 7.2 x 10-4 M
12. Which solution is an acidic buffer?
|
a) |
0.1 M HI and 0.1 M NaI |
HI: Ka = 3 x 109 |
|
b) |
0.1 M HCN and 0.1 M NH3 |
HCN: Ka = 6 x 10-10 |
|
c) |
0.1 M HCl and 0.1 M NaOH |
HCl: Ka = 1 x 106 |
|
d) |
0.1 M NH3 and 0.1 M NH4NO3 |
NH3: Kb = 1.8 x 10-5 |
|
e) |
0.1 M HNO2 and 0.1 M NaNO2 |
HNO2: Ka = 5.1 x 10-4 |
13. In which pair is the STRONGER Acid listed first ?
|
a) |
HCl |
or |
HI |
|
b) |
H2O |
or |
HF |
|
c) |
NH3 |
or |
NH4+ |
|
d) |
HOCl |
or |
HOClO3 |
|
e) |
H3PO4 |
or |
H2PO4- |
14. What is the pH of a solution, which is 0.5 M in CH3COOH (HOAc) and 0.5 M in NaCH3COO (NaOAc)?
CH3COOH: Ka = 1.8 x 10-5
a) 2.9
b) 4.7
c) 5.9
d) 7.0
e) 8.9
15. What is the pH of a solution, which contains 0.729 g of HCl in 250 mL ?
a) 0.14
b) 0.60
c) 1.1
d) 1.7
e) 2.3
16. What is the balanced equation for the base dissociation reaction of pyridine, C5H5NH, in water?
|
a) |
C5H5NH(aq) + H2O(l) |
® |
C5H5N-(aq) + H3O+(aq) |
|
b) |
C5H5NH(aq) + H2O(l) |
® |
C5H5NH2+(aq) + OH-(aq) |
|
c) |
C5H5NH(aq) + H2O(l) |
® |
C5H5NH32+(aq) + O2-(aq) |
|
d) |
C5H5NH(aq) + H2O(l) |
® |
C5H5NH2+(aq) + H3O+(aq) |
|
e) |
C5H5NH(aq) + 2 H2O(l) |
® |
C5H5NH32+(aq) + 2 OH-(aq) |
17.
BONUS: What is the pH of a 0.1 M KNO2 solution?a) 2.1
b) 5.8
c) 7.0
d) 8.2
e) 11.9