SI Exam II Review
Supplemental Instruction
Iowa State University / Leader: / Ryan Gale
Course: / Chem 178
Instructor: / Burnett/Raker
Date: / 3/10/13

1.)Stronger acids are related how to the equilibrium constant? Choose all that apply.

  1. Larger Ka
  2. Smaller Ka
  3. Larger Kb
  4. Smaller Kb

2.)Which of the following acids is the strongest?

  1. HCN pKa = 9.31
  2. CH3COOH pKa = 4.74
  3. HNO2 pKa = 3.35
  4. HF pKa = 3.16

3.)A 0.020 M solution of niacin (a monoprotic acid) has a pH of 3.26. Calculate the percent ionization of the acid.

  1. 36%
  2. 0.61%
  3. 1.6%
  4. 2.7%

4.)In general, for polyprotic acids, what can be said about the dissociation of the acid’s constituent protic hydrogens?

  1. Kb1 > Kb2.
  2. Ka1> Ka2
  3. Ka1< Ka2
  4. The amount of dissociation depends on the character of the polyprotic acid.

5.)Which of the following salts will be acidic in water?

  1. LiBr
  1. Zn(NO3)2
  1. NH4Cl
  1. Na2S

6.)Predict whether Na2HPO4 forms an acidic solution or basic solution. For HPO42-, Ka = 6.2 * 10-8.

  1. Acidic solution
  2. Basic solution
  3. Neutral solution

7.)Indicate whether the following statements are true or false. If false, correct it:

  1. Acid strength in a series of H-X molecules increases with larger sizes of X.
  1. For acids of the same general structure but differing electronegativies of the central atom, acid strength decreases with increasing electronegativity of the central atom.
  1. The strongest acid known is HF because fluorine is the most electronegative element.

8.)How do Lewis acids react with Lewis bases?

  1. Lewis acids accept the electrons that Lewis bases donate.
  2. Lewis acids donate the electrons that Lewis bases accept.
  3. Lewis acids accept the hydrogen ions that Lewis bases donate.
  4. Lewis acids donate the hydrogen ions that Lewis bases accept.

9.)If an unknown salt solution has a pOH of 5.20, what is the identity of the salt?

  1. KBr
  2. LiF
  3. NH4Cl
  4. Ca(ClO4)2

10.)An ammonium chloride-ammonia buffer has a pH of 9.20. Which of the following changes will cause the pH to decrease?

  1. Dissolving a small amount of solid CH3COONa.
  2. Adding a small amount of dilute HCl solution.
  3. Adding a small amount of dilute NaOH solution.
  4. Dissolving a small amount of solid NaCl.
  5. Dilute the buffer solution with water.

11.)Which of the following solutions would you expect silver bromide to have the lowest solubility?

  1. Pure water
  2. 0.020 M NaBr
  3. 0.10 M AgNO3
  4. 0.15 M KBr
  5. 0.10 M LiBr

12.)In a titration of a weak base (B) and a strong acid (HCl), what would the properties of the solution at the equivalence point correspond to?

  1. Cl-, HB
  2. H+, HB
  3. Cl-, H+
  4. BH only

13.)Will silver (I) sulfate precipitate when 100 mL of 0.050 M silver (I) nitrate is mixed with 10. mL of 5.0 * 10-2 M sodium sulfate solution?

  1. Yes, because Qsp < Ksp
  2. Yes, because Qsp > Ksp
  3. No, because Qsp > Ksp
  4. No, because Qsp < Ksp

14.)Codeine, C18H21NO3 is a weak organic base. A 5.0 * 10-3 M solution of codeine has a pH of 9.95. Calculate the value of Kb and the pKb for this base.

15.)A buffer, consisting of H2PO4- and HPO4-helps control the pH of physiological fluids. Many carbonated soft drinks also use this buffer system. What is the pH of a can of a soft drink in which the major buffer ingredients are 6.5 g of NaH2PO4 and 8.0 g of Na2HPO4 per 355 mL of solution?

16.)Predict whether the equivalence point of the following titrations is below, above, or at pH = 7. Write out the neutralization reaction that occurs as well.

  1. Formic acid titrated with NaOH
  1. Calcium hydroxide titrated with perchloric acid
  1. Pyridine titrated with nitric acid

17.)A 50.0 mL solution of 0.200 M HClO is titrated with 0.200 M NaOH solution. Calculate the pH after the following volumes of base have been added:

  1. 25.0 mL
  1. 50.0 mL
  1. 80.0 mL

18.)Calculate the molar solubility of Ni(OH)2 when buffered at pH = 10.0.

19.)A 1.0 M Na2SO4 solution is slowly added to 10.0 mL of a solution that contains 0.20 M Ca2+ and 0.30 M Ag+.

  1. Which of the following compounds will precipitate first:

CaSO4 (Ksp = 2.4 * 10-5) or Ag2SO4 (Ksp = 1.5 * 10-5)?

  1. How much Na2SO4 solution must be added to initiate the precipitation?

Formulas:

R = 0.0821 L atm/K mol = 8.314 J/mol K

T (K) =T (°C) + 273.15

Kw = 1.0 × 10-14at 298 K

Kw = Ka × Kb

pH = -log[H+]

pH + pOH = 14.00

pH = pKa + log