Which of the two structures $A$ $(CH_3COOH)$ and $B$ $(CH_3COO^-)$ given below is more stabilised by resonance? Explain.

(B) $(CH_3COO^-)$ is more stabilised by resonance.
$A$: Resonance structures of $CH_3COOH$:
In structure $(II)$,there is a separation of charge,which increases the energy and decreases the stability of the molecule. Therefore,there is less stabilisation in structure $A$.
$B$: Resonance structures of $CH_3COO^-$:
Both resonance structures $(x)$ and $(y)$ of the acetate ion are equivalent (they have equal energy). Equivalent resonance structures contribute equally to the resonance hybrid,leading to significant stabilisation. Thus,structure $B$ is more stable than structure $A$.