Question

The compound methylamine, CH3NH2, is a weak base when dissolved in water. Write the Kb expression for the weak base equilibrium that occurs in an aqueous solution of methylamine:

Answer 1

Kb = [CH₃NH₃⁺] × [OH⁻] / [CH₃NH₂]

Step-by-step explanation:

According to Brönsted-Lowry acid-base theory:

• An acid is a substance that donates H⁺.
• A base is a substance that accepts H⁺.

When methylamine reacts with water, it behaves as a Brönsted-Lowry base, according to the following reaction.

CH₃NH₂(aq) + H₂O(l) ⇄ CH₃NH₃⁺(aq) + OH⁻(aq)

The basic equilibrium constant (Kb) is:

Kb = [CH₃NH₃⁺] × [OH⁻] / [CH₃NH₂]