Answer is: They are often amines.
For example, solution of methylamine (CH₃NH₂) in water.
Balnced chemical reaction:
CH₃NH₂(aq)+ H₂O(l) ⇌ CH₃NH₃⁺(aq) + OH⁻(aq).
According to Bronsted-Lowry theory acid are donor of protons and bases are acceptors of protons (the hydrogen cation or H⁺).
Methylamine (CH₃NH₂) is Bronsted base and it can accept proton and become conjugate acid (CH₃NH₃⁺).
