Question

Why urea is a monoacitic base?

Answer 1

The amine group (-NH2) in urea can accept a hydrogen ion, making it a basic substance. However, the carbonyl group (-C=O) offers a significant opportunity for resonance, which will stabilise the amine group. This means, urea is very slightly basic (and very close to neutral).

The strength of its basic nature can be measured by its pKb value. Wikipedia says it’s 13.9 , which makes it (for all purposes) a neutral substance. The pKb of a neutral substance is close to 14.0 at RTP. Theoretically, a 0.100 mol dm−3 of urea has a pH of 7.05 .