\(a,4Na+O_2\xrightarrow{t^o}2Na_2O\\ b,Mg+2HCl\to MgCl_2+H_2\\ c,6NaOH+Fe_2(SO_4)_3\to 3Na_2SO_4+2Fe(OH)_3\downarrow\)
\(a.4Na+O_2-^{t^o}\rightarrow2Na_2O\\ b.Mg+2HCl\rightarrow MgCl_2+H_2\\ c.6NaOH+Fe_2\left(SO_4\right)_3\rightarrow3Na_2SO_4+2Fe\left(OH\right)_3\)