Consider hydrolysis with water: ethanoyl chloride (I), ethanoic anhydride (II), ethyl ethanoate (III), ethanamide (IV). The correct order of ease of hydrolysis is

Reactivity toward nucleophilic acyl substitution follows the leaving-group ability and the lack of resonance donation to the carbonyl: $\mathrm{Cl}{}^{-}$ is the best leaving group, then carboxylate, then alkoxide, then the amide nitrogen (best donor). The order is acyl chloride $>$ anhydride $>$ ester $>$ amide.