1. Identify the conjugate bases corresponding to the following acids: [Co(NH3)5(OH2)]3+, HSO4–, CH3OH, H2PO4–, Si(OH)4, HS–. Also write the acid-base reaction with water for each acid and label the acid, base, and conjugate acid.
2. Identify the conjugate acids of the bases C5H5N (pyridine), HPO42–, O2–, CH3COOH, [Co(CO)4]–, CN–. Also write the acid-base reaction with water for each base and label the acid, base, and conjugate base.
3. The ions Na+ and Ag+ have similar radii. Which aqua ion is the stronger acid? Why?
4. Predict whether the equilibrium constants for the following reactions should be greater than 1 or less than 1:
(a) CdI2(s) + CaF2(s) → ← CdF2(s) + CaI2(s)
(b) [CuI4]2–(aq) + [CuCl4]3–(aq) → ← [CuCl4]2–(aq) + [CuI4]3–(aq)
(c) NH2–(aq) + H2O(l) → ← NH3(aq) + OH–(aq)
5. Give the equation for the dissolution of SiO2 glass by HF and interpret the reaction in terms of Lewis and Brønsted acid-base concepts.
6. For parts (a), (b), and (c) state which of the two solutions has the lower pH:
(a) 0.1 M Fe(ClO4)2 or 0.1 M Fe(ClO4)3
(b) 0.1 M Ca(NO3)2 or 0.1 M Mg(NO3)2
(c) 0.1 M Hg(NO3)2 or Zn(NO3)2
7. Draw the structure of chloric and chlorous acid and predict their pKa values using Pauling's rules.
8. In the gas phase, the base strength of amines increases regularly along the series NH3 < CH3NH2 < (CH3)2NH < (CH3)3N. Consider the role of the steric effects and the electron-donating ability of CH3 in determining this order. In aqueous solution, the order is reversed. What solvation effect is likely to be responsible?
9. The aqueous pKa values for HOCN, H2NCN, and CH3CN are approximately 4, 10.5, and 20 (estimated), respectively. Explain the trend in these –CN derivatives of binary acids and compare them with H2O, NH3, and CH4. Is –CN electron donating or withdrawing?
10. The hydroxoacid Si(OH)4 is weaker than H2CO3. Write balanced equations to show how dissolving a solid M2SiO4 can lead to a reduction in the pressure of CO2 over an aqueous solution. Explain why silicates in ocean sediments might limit the increase of CO2 in the atmosphere.
11. Draw the structures and indicate the charges of the tetraoxoanions of X = Si, P, S, and Cl. Summarize and account for the trends in the pKa values of their conjugate acids.
12. An electrically conducting solution is produced when AlCl3 is dissolved in the basic polar solvent CH3CN. Give formulas for the most probable conducting species and describe their formation using Lewis acid-base concepts.
13. Order the following cations in terms of increasing Brønsted acidity in water: Sr2+, Ba2+, Hg2+.
14. Consider the three manganese oxides MnO, MnO2, and Mn2O7. One of them is acidic, one of them is basic, and one is amphoteric. Which one is which?
15. For the reactions given below, find ΔH in units of kJ/mol.
C5H5N + SbCl5 → C5H5N–SbCl5
(CH3)2SO + SbCl5 → (CH3)2SO–SbCl5
16. Predict the products and write balanced equations for the following chemical reactions:
a. CH3HgI + HCl
b. SO3 + H2O
c. SO3 + NH3
17. Calculate the enthalpy of reaction for SbCl5 reacting with acetone and dimethylsulfoxide (two common solvents). Which solvent would have the higher donor number?
18. Would you expect Pauling's rules for calculating pKa to work for carboxylic acids? Why or why not?
19. a) Amongst BF3, BCl3, and BBr3, which would be the strongest Lewis acid? Why? b) Which is more basic towards B(CH3)3: Me3N or Et3N? Why?