$A_1: HCOONa$
$A_2: HCOOH$
$A_3: (NH_4)_2CO_3$
$A_5: CO_2$
$A_4: NH_3$
PTHH:
$HCOOC_2H_5+NaOH\xrightarrow{{t^o}} HCOONa+C_2H_5OH$
$HCOONa+HCl\to HCOOH+NaCl$
$HCOOH+NaOH\to HCOONa+H_2O$
$HCOOH+2AgNO_3+4NH_3+H_2O\to (NH_4)_2CO_3+2Ag+2NH_4NO_3$
$(NH_4)_2CO_3+2HCl\to 2NH_4Cl+CO_2+H_2O$
$(NH_4)_2CO_3+2KOH\to K_2CO_3+2NH_3+2H_2O$