Chapter 15 Review
A student titrates 20.0mL of 1.0M NaOH with 2.0M formic acid, HCO2H (Ka=1.8x10-4). Formic acid is a
monoprotic acid.
1. How much formic acid is necessary to reach the equivalence point?
a. 10.0mL
b. 20.0mL
c. 30.0mL
d. 40.0mL
2. At the equivalence point, is the solution acidic, basic or neutral? Why?
a. Acidic; the strong acid dissociates more than the weak base.
b. Basic; the only ion present at equilibrium is the conjugate base.
c. Basic; the higher concentration of the base is the determining factor.
d. Neutral; equal moles of both acid and base are present.
3. Which of the following would create a good buffer when dissolved in formic acid?
a. NaCO2H
b. HC2H3O2
c. NH3
d. H2O
4. In which pH range would a buffer made with formic acid be most effective?
a. 0-2
b. 2-7
c. 7-12
d. 12-14
5. The solubility product, Ksp, of AgCl is 1.8x10-10. Which of the following expressions is equal to the
solubility of AgCl?
a. (1.8𝑥10−10 )2 molar
b.
1.8𝑥10−10
molar
2
−10
c. 1.8𝑥10
molar
d. √1.8𝑥10−10 molar
6. Which of the following expressions is equal to the Ksp of Ag2CO3?
a. Ksp=[Ag+][CO32-]
b. Ksp=[Ag+][CO32-]2
c. Ksp=[Ag+]2[CO32-]
d. Ksp=[Ag+]2[CO32-]2
7. If the solubility of BaF2 is equal to x, which of the following expressions is equal to the solubility
product, Ksp, for BaF2?
a. x2
b. 2x2
c. 2x3
d. 4x3
Use the following to answer questions 8-10:
150mL of saturated SrF2 solution is present in a 250mL beaker at room temperature. The molar
solubility of SrF2 at 298K is 1.0x10-3M.
8. What are the concentrations of Sr2+ and F- in the beaker?
a. [Sr2+]=1.0x10-3M
[F-]=1.0x10-3M
b. [Sr2+]=1.0x10-3M
[F-]=2.0x10-3M
c. [Sr2+]=2.0x10-3M
[F-]=1.0x10-3M
d. [Sr2+]=2.0x10-3M
[F-]=2.0x10-3M
9. If some of the solution evaporates overnight, which of the following will occur?
a. The mass of the solid and concentration of the ions will stay the same.
b. The mass of the solid and concentration of the ions will increase.
c. The mass of the solid will decrease, and the concentration of the ions will stay the same.
d. The mass of the solid will increase, and the concentration of the ions will stay the same.
10. How could the concentration of Sr2+ ions be decreased?
a. Adding some NaF to the beaker.
b. Adding some Sr(NO3)2 to the beaker.
c. by heating the solution in the beaker.
d. By adding a small amount of water to the beaker but not dissolving all of the solid.
11. A student added 1 liter of a 1.0M KCl solution to 1 liter of 1.0M Pb(NO3)2 solution. A lead chloride
precipitate formed, and nearly all of the lead ions disappeared from the solution. Which of the
following lists the ions remaining in the solution in order of decreasing concentration?
a. NO3->K+>Pb2+
b. NO3->Pb2+>K+
c. K+>Pb2+>NO3d. K+>NO3->Pb2+
12. What is the volume of 0.05M HCl that is required to neutralize 50mL of 0.10M Sr(OH)2 solution?
a. 100mL
b. 200mL
c. 300mL
d. 400mL
13. A lab technician wishes to create a buffered solution with a pH of 5. Which of the following acids
would be the best choice for the buffer?
a. H2C2O4
Ka=5.9x10-2
b. H3AsO4
Ka=5.6x10-3
c. HC2H3O2 Ka=1.8x10-5
d. HOCl
Ka=3.0x10-8
Questions 14-17 refer to the following graph:
The following curve is obtained during titration of 100.0mL of 1.0M NH3, a weak base, with a strong acid.
14. Why is the solution acidic at equilibrium?
a. The strong acid dissociates completely, leaving excess H+ in solution
b. The conjugate acid of NH3 is the only ion present at equilibrium
c. The water which is being created during the titration acts as an acid
d. the acid is diprotic, donating two protons for every unit dissociated
15. What is the concentration of the acid?
a. 0.5M
b. 1.0M
c. 1.5M
d. 2.0M
16. What is the pKb of the base?
a. 2.5
b. 4.5
c. 9.5
d. 11.5
17. What ions are present in significant amounts during the first buffer region?
a. NH3 and NH4+
b. NH3 and H+
c. NH4+ and OHd. H3O+ and NH3
Free Response:
1. The value of Ksp for calcium hydroxide is 5.5x10-6 at 25°C.
a. Write the Ksp expression for calcium hydroxide.
b. What is the mass of calcium hydroxide in 500mL of a saturated solution at 25°C?
c. What is the pH of the solution in (b)?
d. If 1.0 mole of OH- is added to the solution in (b), what will be the resulting Ca2+
concentration? Assume that the volume of the solution does not change.
2. A student performs an experiment to determine the concentration of a solution of hypochlorous
acid, HOCl (Ka=3.5x10-8). the student starts with 25.00mL of the acid in a flask and titrates it against
a standardized solution of sodium hydroxide with a concentration of 1.47M. The equivalence point
is reached after the addition of 34.23mL of NaOH.
a. Write the net ionic equation for the reaction that occurs in the flask.
b. What is the concentration of the HOCl?
c. What would the pH of the solution in the flask be after the addition of 28.55mL of NaOH?
d. The actual concentration of the HOCl is found to be 2.25M. Quantitatively discuss whether
or not each of the following errors could have caused the error in the student’s results.
i. The student added additional NaOH past the equivalence point.
ii. The student rinsed the buret with distilled water but not with the NaOH solution
before filling it up with NaOH.
iii. the student measured the volume of acid incorrectly; instead of measuring 25.00mL
of HOCl, only 24.00mL was present in the flask prior to titration.