a)
\(Mn{O_2} + 4HCl\xrightarrow{{}}MnC{l_2} + C{l_2} + 2{H_2}O\)
\(C{l_2} + 2NaBr\xrightarrow{{}}2NaCl + B{r_2}\)
\(B{r_2} + 2NaI\xrightarrow{{}}2NaBr + {I_2}\)
\({H_2} + {I_2}\xrightarrow{{{t^o}}}2HI\)
b)
\(CaC{O_3}\xrightarrow{{{t^o}}}CaO + C{O_2}\)
\(CaO + {H_2}O\xrightarrow{{}}Ca{(OH)_2}\)
\(2NaCl + 2{H_2}O\xrightarrow{{đpdd/cmn}}2NaOH + C{l_2} + {H_2}\)
\(2NaOH + C{l_2}\xrightarrow{{}}NaCl + NaClO + {H_2}O\)
\(Ca{(OH)_2} + C{l_2}\xrightarrow{{}}CaOC{l_2} + {H_2}O\)