$PTHH : CH_3COOH + C_2H_5OH \buildrel{{H_2SO_4 đ,t^o}}\over\rightleftharpoons CH_3COOC_2H_5 + H_2O \\ n_{CH_3COOH} = \dfrac{3}{60} = 0,05(mol) \\ n_{C_2H_5OH} = \dfrac{2,5}{46} = 0,054(mol) \\ Ta có : n_{C_2H_5OH} > n_{CH_3COOH} \to C_2H_5OH dư \\ n_{ CH_3COOC_2H_5 } = n_{CH_3COOH} = 0,05(mol) \\ m_{este} = 0,05.88 = 4,4(gam) \\ m_{este(tt)} = 4,4.0,9 = 3,96(gam)$