Problems and exercisesAcid-Base Properties

1. From pK_b to pK_a

The pK_b of methylamine is 3.4. What is the pK_a of the methylammonium ion? And that of the anilinium ion, if the pK_b of aniline is 9.4?

2. Order by basicity

Order from most to least basic in water: ammonia, methylamine, dimethylamine, trimethylamine and aniline.

3. Which way does the equilibrium lie?

State which way each equilibrium lies:

1. CH₃NH₂ + CH₃COOH ⇌ CH₃NH₃⁺ + CH₃COO⁻ (pK_a of acetic acid = 4.8)
2. (iPr)2NH + CH₃CH₂CH₂CH₂Li ⇌ (iPr)2N⁻ Li⁺ + CH₃CH₂CH₂CH₃
3. C₆H₅NH₃⁺ + HO⁻ ⇌ C₆H₅NH₂ + H₂O

4. Acid-base extraction

An ether solution contains cyclohexylamine and cyclohexanol. How would you separate them?