a)
\(4P + 5{O_2}\xrightarrow{{{t^o}}}2{P_2}{O_5}\)
\(3{H_2}O + {P_2}{O_5}\xrightarrow{{}}2{H_3}P{O_4}\)
\(3NaOH + {H_3}P{O_4}\xrightarrow{{}}N{a_3}P{O_4} + 3{H_2}O\)
b)
\(F{e_3}{O_4} + 4{H_2}\xrightarrow{{{t^o}}}3Fe + 4{H_2}O\)
\(3Fe + 2{O_2}\xrightarrow{{{t^o}}}F{e_3}{O_4}\)
\(F{e_3}{O_4} + 4CO\xrightarrow{{{t^o}}}3Fe + 4C{O_2}\)
\(Fe + 2HCl\xrightarrow{{}}FeC{l_2} + {H_2}\)
c)
\(S + {O_2}\xrightarrow{{{t^o}}}S{O_2}\)
\(2S{O_2} + {O_2}\xrightarrow{{{V_2}{O_5},{t^o}}}2S{O_3}\)
\(S{O_3} + {H_2}O\xrightarrow{{}}{H_2}S{O_4}\)
\(2Al + 3{H_2}S{O_4}\xrightarrow{{}}A{l_2}{(S{O_4})_3} + 3{H_2}\)
