Supplemental Instruction
Iowa State University / Leaders: / Kyle and Shealyn
Course: / Chem 178
Instructors: / Burnett and Vela
Date: / 3-9-14

Calculations

  1. Calculate the pH and percent ionization of the weak acid, benzoic acid (C7H6O2), if the initial concentration of the acid is 0.2M and Ka = 6.5 x 10-5 at 25C.
  1. Calculate Kb for the weak base CH3NH2 which has a concentration of 0.25M and a pH of 12.
  1. What is the pH of a 0.1M ammonia solution if its Kb value is 1.75 x 10-5?
  1. When hydrogen chloride reacts with ammonia, ammonium chloride is formed. Which is the Lewis acid and which is the Lewis base?

HCl + NH3↔NH4Cl

  1. What is the concentration of OH- in a solution that is 0.3M sodium acetate and 0.5M acetic acid? Ka=1.7 x 10-5 and Kb=5.9 x 10-10
  1. Calculate the pH if 10mL of 0.5M of HCl is added to a 0.1L buffer solution of 0.2M sodium benzoate and 0.4M benzoic acid. Ka = 6.3 x 10 -5
  1. If 10 mmole of NaOH is added to a 100mL solution of 0.02M formic acid what is the final pH? pKa of formic acid = 3.77
  1. Using the following titration of 0.050 L of a 0.100 M HBr acid solution using 0.250 M NaOH.
  2. What is the pH before the titration begins?
  3. What is the pH after 50.00 mL of NaOH is added?
  1. In a solution of 0.200M NaI, solid AgI was placed in. Calculate the molar solubility of AgI (Ksp = 1.5 x 10-16)
  1. Solid barium phosphate dissolves into its ions at room temp. If [Ba2+] = 1.5 x 10-2 M at equilibrium find the value of Ksp.
  1. Calculate the Ksp of Ag2S if the solution contains [S2-] = 2.92 x 10-17 at equilibrium.
  1. Calculate the solubility of Zn(OH)2 in mg/L. Ksp = 4.5 x 10-17
  1. Calculate the concentration of an aqueous solution of Ca(OH)2 that has a pH of 10.05
  1. The pH of a 0.100 M solution of formic acid, HCOOH, at 25 degrees Celsius is 2.38. Calculate Ka for formic acid at this temperature.
  1. What is the pH of a 0.300 M solution of methylamine? (Kb = 4.4x10-4)
  1. Will the following solutions be acidic, basic or neutral?
  2. Ba(CH3COO)2
  3. NH4Cl

c.  Al(ClO4)

  1. NaCl
  1. Arrange the compounds in order of increasing acid strength:
  2. AsH3, HBr, KH, H2Se
  1. H2SO4, H2SeO3, H2SeO4
  1. Circle the stronger acid:
  2. a. HClO3 HClO4
  3. b. HBr HF
  4. c. PH3 H2S
  5. d. HNO3 HNO2
  6. What is the pH of a 1L solution made by adding 0.4 mol of acetic acid and 0.3 mol of sodium acetate to water?
  1. What is the percent ionization of 0.0075M butanoic acid in a solution containing 0.085M sodium butanoate?
  1. You are asked to prepare a pH = 3.00 buffer solution starting from 1.25L of 1.00M HF solution, and excess NaF. How many grams of NaF should be added to prepare the buffer?
  1. What is the pH of the buffer if 85 mL of 0.13M lactic acid and 95 mL of 0.15M sodium lactate are mixed?
  1. Calculate the pH of the solution formed when 45 mL of 0.100M NaOH is added to 50 mL of 0.100M CH3COOH (Ka = 1.8 x 10-5)
  1. Write the expression for the solubility-product constant for the following:
  2. SrSO4
  3. Fe(OH)2
  1. The Ksp value for LaF3 is 2 x 10-19. What is the solubility of LaF3 in water in moles per liter?
  1. How much 2M HCl must be added to 150mL of 0.3M ammonia in order to reach equivalence? What is the volume of the solution at equivalence?

Concepts

  1. How does the strength of the H-X bond affect acid strength?
  1. There are two reasons for an oxyacid’s strength to increase what are they?
  1. What must a Lewis base have?
  1. What is the common ion effect?
  1. What is a buffer solution? Describe what it does and what its components are.
  1. What is buffer capacity?
  1. What two changes of a transition metal will cause its Ka value to increase?
  1. Does the strength of the acid or base determine the volume of titrant to reach the equivalence point? If not what does?
  1. In the titration of the weak polyprotic acid H3PO4 and a strong base it takes 15mL to remove the first H+. What volumes will remove the second and third H+?
  1. Sketch a graph of what this titration would look like. Label the axes, equivalence points, buffer zones (with the buffer components), and the equivalence volumes.
  1. How does the titration curve of a strong acid and strong base differ from a weak acid and a strong base?
  1. Acetic acid is mixed with enough NaOH to reach equivalence. How would the amount of base needed to reach equivalence change if HCl was used instead of acetic acid?
  1. Is a compound with a pKa of 5.1 more acidic or less acidic than a compound with a pKa of 8?
  1. Given that the Ka value for acetic acid is 1.8 x 10-5 what is the pKb value for the acetate ion?
  1. Why are carboxylic acids acidic?
  1. What are an acid and a base according to each definition?
  2. Arrhenius
  3. Bronsted-Lowry
  4. Lewis
  5. What does Ksp stand for? If the Ksp value of a salt is large what does that mean for the salt?