Gọi $n_{HCOOCH_3} = n_{HCOOC_6H_5} = a(mol)$
Suy ra :
$60a + 122a = 18,2 \Rightarrow a = 0,1$
$n_{NaOH} = 0,2.2 = 0,4(mol)$
$HCOOCH_3 + NaOH \to HCOONa + CH_3OH$
$HCOOC_6H_5 + 2NaOH \to HCOONa + C_6H_5ONa + H_2O$
$n_{H_2O} = n_{HCOOC_6H_5} = 0,1(mol)$
$n_{CH_3OH} = n_{HCOOCH_3} = 0,1(mol)$
Bảo toàn khối lượng :
$m = 18,2 + 0,4.40 - 0,1.18 - 0,1.32 = 29,2(gam)$