Question

Which one is more acidic?

Answer 1

This structures are refers to the image$.$

In case of acetamide $,$ the most acidic hydrogen of acetamide is ${NH}_2.$ The conjugate base formed by removed of this hydrogen is more stable because nitrogen has larger electronegativity than carbon $.$ On the other hand $+I$ effect of methyl group in acetic acid decrease the acidity of acetic acid$.$ It pushed the electrons to the carbonyl carbon$.$ And electronegativity of electron is less than oxygen$.$

But the amide could be changed to a carbonylic acid $($acedic acid$)$$,$ which is more acidic because Oxygen is more electronegative than Nitrogen$.$