a,
X: $Cl_2$
$MnO_2+4HCl\to MnCl_2+Cl_2+2H_2O$
$3Cl_2+6KOH\buildrel{{t^o}}\over\to 5KCl+KClO_3+3H_2O$
$KClO_3+6HCl\to KCl+3Cl_2+3H_2O$
$KCl+H_2SO_4\buildrel{{t^o}}\over\to KHSO_4+HCl$
$MnO_2+4HCl\to MnCl_2+Cl_2+2H_2O$
$Cl_2+2NaOH\to NaCl+NaClO+H_2O$
b,
X: $Cl_2$
Y: $NaCl$
$2KMnO_4+16HCl\to 2KCl+2MnCl_2+5Cl_2+8H_2O$
$Cl_2+H_2O\rightleftharpoons HCl+HClO$
$Fe+2HCl\to FeCl_2+H_2$
$2FeCl_2+Cl_2\to 2FeCl_3$
$FeCl_3+3NaOH\to Fe(OH)_3+3NaCl$
$Fe(OH)_3+3HCl\to FeCl_3+3NaCl$
$FeCl_3+3NaOH\to Fe(OH)_3+3NaCl$
$2NaCl+2H_2O\buildrel{{đpmn}}\over\to 2NaOH+H_2+Cl_2$
$2NaOH+Cl_2\to NaCl+NaClO+H_2O$